Acme Thread Dimensions

THE NATIONAL BUREAU OF STANDARDS Functions and Activities The functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials, devices, and structures; advisory services to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic and applied research, development, engineering, instrumentation, testing, evaluation, calibration services, and various consultation and information services. 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There are also five series of nonperiodical publications: Monographs, Applied Mathematics Series, Handbooks, Miscellaneous Publications, and Technical Notes. Information on the Bureau's publications can be found in NBS Circular 460, Publications of the National Bureau of Standards ($1.25) and its Supplement ($1.50), available from the Superintendent of Documents, Government Printing Office, Washington 25, D.C. UNITED STATES DEPARTMENT OF COMMERCE; NATIONAL BUREAU CF STANDARDS • .j FREDERICK H. MUELLER, Secretary ,A. V. ASTW, Director NATIONAL BUREAU OF STANDARDS HANDBOOK H28 (195 7) SCREW-THREAD STANDARDS FOR FEDERAL SERVICES 1957 PART III ACME, STUB ACME, AND BUTTRESS THREADS ROLLED THREADS FOR SCREW SHELLS OF ELECTRIC LAMP HOLDERS AND UNASSEMBLED LAMP BASES MICROSCOPE OBJECTIVE AND NOSEPIECE THREADS SURVEYING INSTRUMENT MOUNTING THREADS PHOTOGRAPHIC EQUIPMENT THREADS ISO METRIC THREADS; MISCELLANEOUS THREADS CLASS 5 INTERFERENCE-FIT THREADS, TRIAL STANDARD WRENCH OPENINGS DTIC QUALITY INSPECTED 3 Amends in part H28 (1944) (and in part its 1950 Supplement) [Issued Oc ober 7, 1960] of Commerce HI Accasion For NTIS CRAM OTIC TAB Unannounced Justification By Diät »button/ Availability Code» Oist Avail and/or Special a D M . on screw-thread standards for Federal Services. For the Secretary of Defense. submitted by the Interdepartmental Screw Thread Committee. is hereby approved for use by the Departments of Defense and Commerce.* APPROVAL EX THE SEC FBI ARIES OF DEFENSE AND COMCRCE The accompanying Handbook H28 (1957). Part III. SECTION XIX. British standard for microscope objective and nosepiece threads Surveying instrument mourning threads . Thread.. Gagtti. 1. British standard Buttress thread jJü.. ISO thread profiles 2. Shutter cable release tip and socket with straight (American) thread (PH3. Standard series for ISO metric threads 3.Specifications j. Bibliography. SECTION XI\ .10) 4. 1.. Acme threads. torques. r 4. Specifications for Stub Acme form of thread 3.eral and historical 2.7).. Shutter cable release tip and socket with taper (European) thread (PH3. General and historical 2. Limits of size.. 1.-i. . The tightening of threaded fasteners to proper tension 1.. ii in 1 1 4 6 7 10 10 10 17 18 18 18 18 19 19 20 21 22 SECTION XIII. Design and application data 4. 1I .^5eneral. 0. Class 5 interference-fit threads.. _ 6.. standard Stub Acme threads 6.i.6) 2. °r>. Standard Acme thread se4.. Glass bottle and jar threads. 1. /t—• 20UNC—1A/1B threads (PH3. Generahand historical i.. 3. Fartfj of flireacT-.. 1. Tnrfcad series'. Thread designations 7.. SECTION XV. 4... Scope 3..Historical.«. Photographic equipment threads. _.12) _ 5. Appendix 10. . Tripod connections l for American cameras. Bibliography on measurement of pitch diameter by means of wires Appendix 14. L .23). Specifications \--t- 27 27 27 27 27 28 28 32 33 34 54 54 54 55 59 59 60 61 61 62 62 3-1 34 34 35 36 36 36 38 38 40 40 40 40 —X-fiaae dilafipaamü SECTION XVII..(e) GaKinatoensfonb^. 4. 'atltffral Buttress threads. SECTION XII. Thread designations 7.. • C I I II If IT! It ^m ii i »i «^pn^3i ■ ■ —•— — ^»» — . standard Stub Acme threads 5. General and historical 2. Buttress threads 3... Gages for Stub Acme threads _ (a) Gage tolerances (b) Gages for external threads • (e) Gagea for iutej'ual tnteads.lamp-hokjers-and for-awew «l^eljs» of unassembled lamp '"bases" ' '1 i. Acme and Stub Acme threads. Gage dimensions L. Angular turn of nut method 5. 6. .'r. Tables of dimensions.. Three-wire method of measurement of pitch diameter of 29° Acme.._~ ■__ Microscope objective i and noseSECTION XV piece thrqads. 3.*^. Tripod connections for European cameras: Y»— 16UNC—1A/1B (PH3. "Feel" method. Introduction 2. 2.designations :. and Buttress threads 1. '" 1. Wrench openings Appendix 11.«. IV .-.. Modified square threads 3. p$y_ . 2. Nat. TT. Standard Stub Acme thread series 4. 3. Micrometer method 2.. Designations for ISO metric threads 41 41 42 42 42 45 45 45 45 45 46 46 47 48 48 48 48 52 52 52 52 53 53 53 53 53 25 25 26 r.. Threads for attaching mounted lenses to photographic equipment (PH3. Alternative Stub Acme threads 8.. 1. 60° stub threads 2... Specifications 3. J-. 4. Appendix 13. and interferences 5.80Q—36AM[). Specifications for Acme form of thread 3. (a) Single-start external threads (b) Multiple-start external threads (c) Limitations of threewire measurement of external threads 2. Attachment threads for lens accessories (PH3. Acme threads 5. Threads for dairy sanitary fittings "..-?'. Metric screw-thread standards 1.*.24) . Classification and tolerances. XVIII. Extension of the standard Appendix 12.. 3. Torque measurement method. "i.--. Use of special devices for controlling tension 6.... —ÄnTeTiüKh Ständard rolled threads for screw shells ef electric . ■ i .AT-!.1. Limits of size. 2. 29° Stub Acme. Gages for Acme threads (a) Gage tolerances (b) Gages for external threads (c) Gages for internal threads (d) Concentricity Stub n Acme threads 1... Miscellaneous threads. 6. ..'« r__:'. Classification and tolerances.Contents Fags Page SECTION Foreword Personnel of the Interdepartmental Screw Thread Committee Approval by the Secretaries of Defense and Cornmerce Acme threads . Trial American Standard 1. ._... 4. class 2.3.3.—Acme threads series.—Pitch diameter tolerances for Acme screw thread«. NS Table XIX.2. Table 13. 3G.1.13.—Tolerances on Buttress threads.2. axial pitch Acme and Stub Acme threads (29°) Table 13. Acme thread classes Table XII.—Modified Form 1 Stub Acme thread form.5.—Limits of size and tolerances for preferred attachment threads for lens accessories. and lengths of threads for attaching mounted lenses to photographic equipment.—Tolerances on Buttress threads. 1.2.—Limits o'.5. classes 2G. 0. and6C.—Recommended gage dimensions for surveying instrument mounting threads Table XVIII. and torques. 4C.1.—Basic dimensions. and basic and design dimensions.—Pitch diameter compensation for adjusted lengths of "go" ring gages for general purpose and centralizing threads Table XIII.1—Standard wrench openings Table 11. Table XII. Acme threads .—Best wire diameters and constants for large iead angles. 1-in.1. Stub Acme threads Table XIV.—ISO metric screw threads for screws.—Standard Stub Acme thread form.—American Standard rolled threads for lamp holder screw shells _ _. Table XVI. aiid 4G Table XII.—Limits of size and tolerances. lengths of engagement. basic dimensions Table XIII.—ISO metric screw threads for general use. 45°) Table 14. Table 13. classes 4G.7. and allowances. Stub Acme threads.3. classes 3G.1.800—36AMO.8. basic diameters and thread data Table XII. class 3 (close) Table XIV.—Modified Form 2 Stub Acme thread form.25 to 300 mm diameter Table 14. 1.—Interferences. class 5 Table 11. Table XVI.—Pitch diameter tolerances for Acme screw threads.2. Table XIII.6.3. class 2 (medium) Table XIV.—Values of (1 + cosec a') for o= 14°30' and lead angles from 0° to 5° -.. tolerances. 14.—Values for wire measurements of single-start standard Stub Acme threads (29°) Table 13. 0. _ Table XIII. all classes Table XIV.25 to 39 mm diameter 2 3 4 5 6 7 8 9 10 11 13 14 17 17 19 21 22 22 23 25 25 26 26 30 30 30 31 31 34 35 35 37 37 39 39 40 41 43 44 44 46 47 50 50 51 54 55 56 56 57 60 63 65 .3C.1.8. Table XII.9.—Pitch diameter tolerances for Acme screw threads.6—Numerical data for British Standard form Buttress threads Table XV.—Basic dimensions. 3C. 3.—Standard Stub Acme thread series. Table XII. class 2. 12.—Basic dimensions for Buttress threads Table XIV. basic dimensions Table XIII.—Symbols. Stub Acme threads Table XIII.3.1.—Tolerances for "go" and "not go" thread gages.2.1. class 3A/3B UNS _Table XVIII. class 5 Table 11. 0. 2. classes 5Cand6C Table XII.—Limits of size. 36 tpi.—Wire sizes and constants. class 5 Table 13.—Tolerances on Buttress threads. Acme centralizing thread series. Table XII. NS Table XVIII.—Limits of size. 1.5.—Limits of size. classes 2C. external threads.—Limits of size for the British microscope objective and nosepiece thread Table XVII.6.—Values for wire measurements of single-start standard Acme threads (29°)-.—Recommended gage dimensions for microscope objective and no"> piece thread.—Limits of size and tolerances. 0.4.—Tolerances and allowances (minimum clearances) for major and minor diameters.—Pitch diameter allowances for Acme threads Table XII.3. Acme centralizing thread series..—Limits of size and tolerances. bolts.—Tolerances for plain gages. 6. 36 tpi.9. 7.2. standard Stub Acme thread series Table XIII. Acme general purpose thread series. 5. class 1 (free) Table XIV. 4.—Allowances on external Buttress threads. single-start Acme and Stub-Acme threads (29°).4. size and tolerances.—Wire sizes and constants. surveying instrument mounting threads Table XVII. and nuts. tolerances.11. internal threads. formulas.800—36AMO Table XVI. Acme thread series Table XII. classes 2G and 2C_ _ _ Table XII.—Limits of size.Tables Page Table XII. centralizing Acme threads Table XII.—Pitch diameter allowances for Stub Acme threads Table XIII.. single-start Buttress threads (7°.—Basic dimensions of 60° stub threads Table 10.—Formulas for diameters.4. and5C Table XII.800—36AMO Table XVI.—American Standard rolled threads for lamp base screw shells before assembly Table XV.—Limits of size and tolerances for secondary attachment threads for lens accessories.-. Table 13.10. basic diameters and thread data. basic dimensions Table XIII.2 — Limits of size and tolerances.1.—Tolerances and allowances for major and minor diameters.and4C .2. general purpose Acme threads. 0.—Tolerances for "go" and "not go" thread and plain gages.2. Figure 12.2.340 in. 3C.5.1. classes 5C and 6.—Modified square thread (10° included angle) basic proportions Figure 11. Tigure 14. and 4G Figure XII. and tolerances. length screw.10. classes 2G.—Drilling for elongation determination when one end is not accessible.1. %—l6 UNC—IB Figure XVIII.1.1. allowance.2.—Typical arrangement of microscope objective and nosepiece Figure XVI.375 pitch.—Surveying instrument tripod head and base plate Figure XVIII. Buttress threads Figure XIV.1.1 —Tripod screw. Yt—20 UNC--1B Figure XVIII.3 — Spacer for use on tripod with 0. Figure XIX. and root truncations.7.3. Figure 13.—Disposition of tolerances. and 4C __ Figure XII. H—16 UNC— 1A Figure XVIII.—Shutter cable release tip with straight (American) thread Figure XVIII.—Modified Form 1 Stub Acme thread with basic height of 0.2.800— 36AMO thread Figure XVI.—ISO design profile of external and internal threads without an allowance for inch and metric screw threads VI 2 3 12 15 16 20 24 25 25 29 31 34 35 36 38 39 40 41 41 42 42 42 42 44 45 45 45 45 46 49 53 53 59 60 61 62 62 .11. tolerances. tolerances.Figures Page Figure XII. and crest clearances for Stub Acme threads Figure XIII.—Illustration of allowances.C __ Figure XIII.1..—Tripod socket in camera. and crest clearances. 1. American Standard rolled threads for screw shells of electric lamp holders and lamp bases.—Illustration of allowances. 3G.—Illustration of thread form.—Form of Buttress thread having 7° pressure flank and 45° clearance flank Figure XIV. and crest clearances.2.—Illustrations showing maximum and minimum interferences.—Length. and crest clearances for 0.—Basis of lead angle correction for external thread Figure 13. 1. Figure XIV.1.—Diameters of "best" and "maximum" thread wires for Buttress threads.2.4. ^—20 UNC— IB Figure XVIII. and undercut of attachment threads for lens accessories Figure XVIII.3 — Basic form of Whit worth thread Figure XVII.2. tolerances.25 pitch. class 5 threads Figure 12. _ Figure XVI. 1..—Centralizing Acme thread form Figure XII. >i—20 UNC—IB internal thread Figure XVIII.—Standard Stub Acme form of thread Figure XIII. centralizing Acme threads..4.—Thread details for shutter cable release tip and socket with taper (European) thread (50 tpi) Figure XVIII.—Open type shutter cable socket with straight (American) thread.—British Standard form of Buttress th .9. centralizing Acme threads.3. classes 2C.—Illustration of allowances.—Erfective length applicable in elongation formula. pilot. Figure XIII.4—Tripod screw.—Illustration of tolerances. allowances.—Modified Form 2 Stub Acme thread with basic height of 0.—Illustration of allowances. tolerances.3.2.—Shutter cable release tip with taper (European) thread (5U tpi) Figure XVIII.—ISO design profile of external and internal threads with an allowance for inch and metric screw threads Figure 14. and crest clearances.2.1. general purpose Acme threads. %—16 UNC—1A external thread.—General purpose Acme thread form Figure XII.5 —Tripod socket in camera.—ISO basic profile for inch and metric screw threads Figure 14. '4—20 UNO—1A Figure XVIII. allowances.3.'ad Figure XV.8.6— Adapter. 2.1957 HANDBOOK OF SCREW-THREAD STANDARDS FOR FEDERAL SERVICES. this application is highly specialized and these data should not be used without consultation with the valve manufacturer. The line bisecting this 29° angle shall be perpendicular to the axis of the thread. Formulas and data for use with special threads are also provided in table XII. the pitch diameter tol1 This section Is In substantial agreement with American Standards Association publication ASA B1. and 0." which Is published by the A9ME. measured parallel to its axis. between corresponding points on adjacent thread forms. In addition to limits of size for the standard series of diameters and pitches of Acme threads. 8. Stub Acme threads are covered In section XIII.020 in. and 0. and XII. some mechanical means should be provided to eliminate the condition. general purpose and centralizing. Multiple threads should be considered when fast relative motion is required.6. N. 3. etc.—(a) General purpose threads. Acme threads arc now extensively used for a variety of purposes. p.5.020 in.7. A minimum diametrical clearance for the fillet is provided at the minor diameter by establishing the minimum minor diameter of the internal thread O.2 The three classes of general purpose threads have clearances on all diameters for free movement and may be used in assemblies with the internal thread rigidly fixed and movement of the external thread in a direction perpendicular to its axis limited by its bearing or bearings. for pitch diameter allowances on external threads. GENERAL AND HISTORICAL When formulated prior to 1895. A minimum diametrical clearance at the major dip.010 in. G. HEIGHT OF THREAD. The latest revision should be1 consulted when referring to this ASA do« iment. 18. 29 W.—The angle between the flanks of the thread measured in an axial plane shall be 29°.—A minimum diametrical clearance is provided at the minor diameter of all external threads by establishing the maximum minor diameter 0. 2. 38th St.—The pitch of a thread is the distance. The five classes of centralizing threads have a limited clearance at the major diameters of the external and internal threads. pp. PART III As Approved i960 SECTION XII. This is unavoidable for interchangeable product.. below the basic minor diameter for 10 threads per inch (tpi) and coarser. and 0. so that a bearing at the major diameter maintains approximate alinement of the thread axis and prevents wedging on the flanks of the thread.—The basic thickness of the thread at a diameter smaller by one-half the pitch than the basic major diameter shall be equal to one-half of the pitch. 5. In any case. and 9. and the two parts are adjusted to bear on opposite flanks of the thread of the externally threaded member. "Acme Screw Threads.OOlVZ? above the basic major diameter. This section provides for two general applications of Acme threads. p. THICKNESS OF THREAD. New York IS. (6) Centralizing threads. (c) the internally threaded member is split perpendicular to the axis. .—The basic height of the thread shall be equal to one-half of the pitch. tools. 7. SPECIFICATIONS FOR ACME FORM OF THREAD 1.4.5. ACME THREADS1 1. The following practices have been successfully used: (a) The internally threaded member is split parallel with the axis and adjusted and lapped to fit the externally threaded member. A minimum diametrical clearance at the major diameter is obtained by establishing the minimum major diameter of the internal thread 0. (6) the internally threaded member is tapped first and the externally threaded member is milled. For any combination of the five classes of threads covered in this section some end play or backlash will result. ances for special diameters and pitches can be determined for each class. PITCH OF THREAD. and by use of the formulas for diameter and pitch increments shown in tables XII.lp greater than the basic minor diameter.ueter is obtained by establishing the minimum major diameter of the internal thread O. XII.010 in. and in table XII. ALLOWANCE (MINIMUM CLEARANCE) AT MAJOR AND MINOR DIAMETERS. ground. for finer pitches. sufficient end play must be left to provide a close running fit. for major and minor diameter allowances and tolerances. ANGLE OF THREAD.8. 5. namely. for finer pitches. Acme threads were intended to replace square threads and a variety of threads of other forms used chiefly for the purpose of producing traversing motions on machines.Y. tables of pitch diameter tohrances provide for a wide choice of diameters for a given standard pitch. 4. or otherwise machined to fit the internally threaded member. While threads for valve operation may be made to this standard.020 in. above the basic major diameter for 10 tpi and coarser. When backlash or end play is objectionable.010 in. for finer pitches. p. below the basic minor diameter for 10 tpi and coarser.—A minimum diametrical clearance is provided at the minor diameter of all external threads by establishing the maximum minor diameter 0. 75000 1.3433 .04107 . 2000 .5p Crest of internal thread (basic). 7.n = 0.0725 .-v. 0.0411 . For centralizing threads.00 . IIIO0O . F„= 0. 0.-0. 14 12 .'///7// ' Y EXTERNAL v THREAD 7 / / p 77.0927 .050011 .0200 . 1707 . 66607 .5p ance • Thread thickness (basic). 1.08250 .00250 .0371 .33333 .2.0089 ..0407 .0309 .259X (mine .2780 . 3C.3T07p—0.5100 5 in.--diameter allowance on external thread— pitch-diameter allowance on external thread).1431 .5p Ft. 3707 1« .03571 .2. \ x "77/77 //<////>// / MINOR DIAMETER ////// / /. 16607 ..1350 .259X allowance • 7 ill. ■////.0875 . «=0. the basic dimensions for the most generally used pitches are given in table XII."-'■'■ ////„7/7■■''■■ '■•'/ v/Yv///////.0500 . 12500 ..33 . 211000 ..—External threads shall have the crest corners chamfered at an angle of 45° with the axis to a minimum depth of 0.12500 .1483 . cols.03125 . F. ?7/ '///^k .6. W. the basic thread form is symmetrical and is illustrated in figure XII.3707p0. 251. TABLE XII.1. .08333 .259X(major-diameter allowance on internal thread) >'r.25000 . n Pitch. B /A' • < . 0000 .05000 . // . y////// // / '/■/ .1/>.0302 . BASIC DIMENSIONS.200110 . . P Total Height of height of thread.00250 .1184 . M07 . 10 8 6.1(11167 . (b) Centralizing threads. \~y-isa5P—«JkfoFcn^7A/'>.0707p and a maximum width of 0.) External threads for classes 2C. thread (basic).—(a) General purpose threads. 1IXKX) .4.0945p..50000 VA.05^ and a maximum depth of 0. CHAMFERS AND FILLETS. see table XII.37500 .11714» .1853 .37300 50000 6 in.lp and for classes 5C and 6C the minimum fillet shall be 0.—General purpose Acme thread form.3707p=basic width of flat of crest of external thread F. 2a-=29° a=14°30' p-pltch n»=number of threads per inch AT-number of turns per inch A'basic height of thread=0. This corresponds to a maximum width of chamfer flat of 0.0945p. 1.3707p Hoot of internal thread.5p (-thickness of thread=0. 1 i For allowance. 0.401100 . This corresponds to a minimum width of chamfer flat of 0. 5 4 3 ill. NOTATION FlGUBE XII. 3.00000 o 4 in. 0. and 4C may have a fillet at the minor diameter not greater than O.3655 1 2 in.=0. 9 IK IM--.—External threads may have the crest corners chamfered at an angle of 45° with the axis to a maximum depth of 0.. • ' '' i ALLOWANCE CW—' •' ■ ^^7/n^77^S^7^/..5 allowA=0.=ft+0.0239 . 1236 .2728 .2YYZJ^ //// 77// /1\ V \\ \ \\VVY/.10571 . A. 50000 .Y/W7■ 7 (SCREW) Y7/7 7/< /// / /.■.—(<z) General.1100 .20000 . 0933 .0667p.-~. Mtf'7^/7 /77?77/xffl<''/ //////SAY7--Y///////7// 'X /. 6 and 7. 0403 . / 7//.06p. the basic thread form dimensions for the most generally used pitches are given in table XII. 12500 . col. general purpose Acme threads Width of flat at: Threads per Inch.. and the maximum fillet 0.l--Basic dimensions.3707p-basic width of flat of crest of Internal thread F„-0.33333 .0741 .0283 . Internal threads of all classes may have a fillet at the major diameter not greater than 0. A ALLOWANCE OAM //A/ ' /PITCH DIAMETER '..0407 .07p.03125 . 0205 .210(1 .0319 .04107 .3850 .2419 .33. 10000 .0667p. 2471 .2. 25(100 .1802 .0232 .08333 .3707p—0. 0.=0.08333 .—For general purpose threads. the basic thread form is symmetrical and is illustrated in figure XII. (See table XII.0018 . 0. 0330 . 0280 .25000 .16667 . 0. FIOIRE XII.12500 .0125 .0707p Max fillet radius. 0. sec table XII.5p Total height of thread (all external threads) A.50000 4 in..0120 .TABLE XII.0280 .0080 . 0.5100 5 in.„«0. 0030 . 66067 .0060 .«0.0044 .0167 . 0. («170 .2100 .3707p-baslc width of flat of crest of external thread F.0300 .0933 .0058 .0050 .0667 .10000 .(KIOO . 0070 .0031 .33333 .0180 .=ft+0.0140 . 0. 1767 .0050 .0710 8 in.03125 .08333 .0240 . 3.5 p (-thickness of thread»0.5 allowance * 1 2 in.0600 16 14 12 10 g 6 5 4 3 2H 2 1 m 114 ' For allowance. centralizing Acme threads 45° chamfer crest of centralising external threads Thread thickness (basic).0240 .25000 .5p Min depth.0200 .0083 . 0.0120 . root of centralizing tapped hole.0150 .0600 .75000 1.0350 .0233 .0140 .0500 .0071 ..0362 .08333 . 16667 .06250 .0467 . 0O02 .0062 .0100 .0125 . NOTATION 2a-29° a= 14°30' p-pitch n=numlxr of threads per Inch A7-number of turns per Inch » = basic height of thread-0.37500 .0200 . 0.20000 .0175 .12500 .0400 .0088 .3433 .2ä»X(minor-diameter allowance on external thread—pitch-diameter allowance on external thread).3707p-0.20000 . 16667 .0044 . 0525 .0407 .0450 .66250 .05. A=0.0350 .06000 .0075 .0083 . 25000 .33333 .25»X(maJor-di9rueter allowance on internal thread) Fr.0050 .0470 .0040 . . 0.04167 .0725 .07p 9 in.00p Fillet radius at minor diameter of centralizing screws Min (classes 5 and 6 only).0467 . col.05000 .60000 ..33333 .—Centralizing Acme th-ead form. 0. 50000 0 in. i=0.0040 . Mln width of chamfer Hat.3850 . 0.06250 .0500 in.p Height of thread (basic).03571 .2600 .0117 . 0.40000 .1000 Threads per inch.0750 .00000 3 in.0167 . Pitch."=0. 0200 .10000 .(0125 .4.0-:O0 .0260 .20000 .-0J707p-basic width of flat of crest of Internal thread F.04167 . 0.'2500 ."380 . are measured from the intersections of the straight flanks and roots.1100 .0050 .07143 .37500 .0042 .0700 Max (all classes).08333 .03571 .0100 .0333 . r.2. 0.5 p F«. Fm and F.1360 . 0250 .0530 .10p 10 in.0100 .10000 . 0.2—Basic dimensions.3707p-0. 2207 1. 1220 1. ft— eter. . XII. specifications.. TABLE «CJ 1 6C These classes.4441 4 3 4 33 3 50 4 3 3 33 3 10 3 39 3 19 2 2 2 2 2 48 26 55 36 21 4 12 4 42 3 57 4 10 3 39 3 15 3 44 3 23 2 2 2 2 2 3 2 2 2 1 52 29 58 39 23 22 51 28 10 56 m m 1M 1H 1H .1287 .08333 . 372 2.7500 3.0232 .8750 9985 1.(W333 .7169 1. n=0.350 .0927 .5+n tun 14h° (/■'.3707p (leneral purpose. ..788 5.2500 4.983 2. classes >C and 6C Nomisizes (all classes) nal Threads per Inch.9167 2.07143 . 1500 1.eter. 0.2194 1. 0. classes 2C.7146 1.4.7500 3. and 4C.11474 .3.0220 1.298 1. and 4C Cent ralizing. . and classes 5C and 6C for centralizing threads only.VXJ .9750 1.56000 . (2) better manufacturing control of the machined size due to greater ease of checking. 16667 .2188 .251X1 2.4000 .5000 4.0618 .837 3.3333 . t'imputed from this formula: Shear areu-i/C[0. and cell» tralbing classes 2C.5000 3. ■> Figures given are tbe minimum stress area based on the mean of the minimum minor and pitch diameters of. 6451 . all classes. X 13 ilttt 5 4 4 3 4 min 12 42 33 50 3 Identification Basic diameters Oeneral purpose.1272 2.1853 .069» . CLASSIFICATION AND TOLERANCES. It may he economically advantageous nnd therefore desirable to have the centralizing control of the mating threads located at the minor diameters.n Pitch Minor Major Minor diamdiamdiamdiamdiamMajor diam.7.11618 . shall have allowances and tolerances in accordance with table XII.. «OHO 3.1022 .2938 2..0309 (1371 . «5000 .786 5.16667 .7284 .545 . 139 2. 9500 4..3 which is recommended as preferred. «625(1 .8.6250 1.1250H .2043 . Iti667 . 25MXI .0285 .67 7. («167 .VX) . 4470 4. shall show the actual basic major diameter in decimals on drawings.0985 1.907 1. (XI27 .25000 .3333. 1970 4.03125 . X Shear area.6667 .5000 .08333 . 0. 0458 2. 5IXXX) 10 in. . KXXII .25000 25IXXI .4375 .6941 0. K= eter.3750 1.1250 1.0000 4.851 2. XII.941 1. 2IXKX) .5833 . 16667 . 3.050O 1.3823 .025 (/<--/» («-2A) Pitch Pitch. 4567 2.1236 .12. --.1853 .5354 ..7683 .4604 1.7917 .53 u ■Me in.4802 . are for the purpose of assuring the interchangeable manufacture of Acme threaded parts.««27 .118333 .5427 .5000 5.3125 .««27 . .04167 .0265 .. 7067 3. 3750 1.4323 .—Special diameters not shown in table XII. 2IXXXI ..83W6 2.7083 .50 10.. 7500 1. 339 1.0000 3.8792 2.5000 1.—Applications requiring special machining processes resulting in a basic diameter other than the nominal diameters shown in table XII.3750 . 3752 2.6. class 30 • Stress area.2500 1.™ 1.2917 . ' When Acme centralizing threads are produced in single units or In very small quantities (and principally in sizes larger than the range of commercial taps and dies) where the manufacturing process employs cutting tools (such as lathe cutting). Each user is free to select the classes best adapted to his particular needs.. It is suggested that external and internal threads of the same class be used together for either general purpose or centralizing assemblies.eter.2500 ..01X10 4.2032 3. lie external thread.7500 . . IIKXX1 .2708 .5p Basic width of flat.5625 . 0. as follows: Type or thread General purpose Centralizing _ 2() 2C Class of thread 30 3C 40 4C There has been selected a scries of diameters and associated pitches of Acme threads listed in table XII.5000 .VX) .25000 . class 301> 1 2 3 4 fit. I25IXI .25000 . basic diameters and thread data Thread data Lead angle at basic pitch diameter Thread thickness at pitch line. classes 3 and 4 are provided for both general purpose and centralizing threads.2500 1. and tools. 501 3.3333 2.1236 1236 .3958 .7085 2.03119 . I25IXI .12 13. «4167 .9250 1. 0.3542 . 2.54 16 sq in.4167 2.03571 .12500 . .3C. HXXXI .5000 in.. P V-Ö) Centralizing classes 5C and 6C.3 or not divisible by Ke. and tabulated tolerances. footnote a.8750 1.03571 . . . 5tx»x> .13 16. (XXX) 2. If less backlash or end play than provided by class 2 is desired. HXXXI .27 7. KKXXI . in order to reduce to a minimum the inventory of both tools and gages.5833 2.3444 1. the advantages cited for minor diameter centralizing control over centralizing control at the major diameters of the mating threads are: (1) Orcater ease and faster checking of machined thread dimensions. D (/>-») (D-2h) (73-0. Oi63 . i 4H 6 . 4669 1.33333 . 9 in.05000 .5000 1. 2500 3.0312? .60 8. Figures given are the minimum shear area based on max A'„ and min K.643 4.-A'. and XII. 451 . 06250 .5» 1. in. and centralizing.7500 2.1250 1.(b) Special requirements (deviations from nominal diameter).9441 0. I=0.4150 . 0. . I2.0250 1. 751 1.5.3333: SIXXXJ . 2125 2.4823 .1667 2. 0.. K= eter.08333 . 6K4» .4532 3.. all classes.660 .2220 1. 250110 .0*57 1.7750 .70» .519 1.301 3. IB 14 12 12 10 8 6 6 S 5 S 4 4 4 4 3 3 3 2 2 2 2 2 0. 12.1875 .049 3.2848 .73 6.870 4.577 4. tables XII.8516 .0000 1. E. (c) Special diameters. 4.08333 . 7 8 in.25000 11 in.10000 .8000 . 0.25000 .7500 5 e in.1853 . It Is much easier to measure the minor diameter (root) of the external thread and the mating minor diameter (crest or bore) of the internal thread than it is to determine the major diameter (root) of the internal thread and the major diameter (crest or turn) of the external thread. Particularly under the above-mentioned type of manufacturing. (3) lower manufacturing costs.»000 1. 8750 2.5p Basic height of thread.1X1250 .04167 .0833 2. 16667 .8985 1. 9532 3. HXXXI . 3C. 5919 1. table XII. together with the accompanying specifications.2411 .9567 3.«741 «741 . 4 13 15 *q in. K= eter. . 2 2M —.1853 .5000 4. 2H a« 3 Hi.3—A erne thread series.5418 2. 6052 .9470 4.1853 14 rfrg min . column 1.9646 2. 45(X) 3.110 4.)].20000 .3457 1.«741 .7500 4. STANDARD ACME THREAD SERIES 3 These diameters and pitches have been carefully selected to meet the present needs with the fewest number of items. ACME THREADS There are established herein three classes of threads for general purpose and five classes for centralizing Acme threads.7000 4.50000 3 1» 2 48 2 26 2 9 1 55 • Per inch length of engagement of the external thread in line with the minor diameter crests of the internal thread. 1251X1 1251X1 1*887 16667 16667 25IIX) 25<XXI 25HX1 25tXX> 2.6250 . F= 0.5000 2. 5617 .VXXJ 12 in. (1.0000 in.749 . 108 1. 41X15 2. H ?<§ M M H H l 0.4500 .. 3.020 . with the minimum tolerance value set at 0.0010 . 1 2 3 in. thread.0200 .020 . Q.0062 .0125 .0035 .0200 .0008 .5 p.0050 .001» . 0055 .0008 .0200 .0012 .imw\/T) 4 in. Similarly.020 in. A class 2C external thread.0083 . all internal threads. 004« .0020 . The minimum minor diameter of the centralizing internal thread is O.020 .0021 .0017 . O. minus on external threads General Purpose Centralizing Size« Threads per inch.1120 . 0052 .0052 .001» . and the major-diameter tolerance on the external thread.0125 .020 .0083 .020 . Tolerance on minor diameter of all external threads is 1.020 .0250 .—(a) The tolerances specified represent the extreme variations allowed on the product. 3 and 6. The requirement for a centralizing fit is that the sum of the major-diameter tolerance plus the majordiameter allowance on the internal thread. ' To avoid a complicated formula and still provide an adequate tolerance. threads. The average backlash for any cross combination will be between the values for backlash when both members are class 5C and when both members are class 6C. established by subtracting 0.05110 . 0074 . but ordinarily may be interpolated.0017 .020 .0250 . 0250 .010 .0014 . minus • Centralizing All classes Class 2C Classes 3C and 5C Classes 4C and 6C Major Major Minor 1 diameter. 0500 .0011 .0068 .020 .020 .020 .0211 . LENGTH OF ENGAGEMENT.020 . 0167 .0028 .0011 .0125 .0250 .0025 .0023 . tUMbs/T) 0.020 . 0107 .020 . M Hi . or 4C internal threads and fulfill this requirement. 001» . 0002 .0083 . the pitch factor Is used as a base.010 .Vll . («150 .0017 . 12 in. 01«7 .008.0037 . 0074 .0037 .004» .020 . NOTE. one diameter long. 14 in.—The maximum major diameter of the external thread is basic and is TABLE the nominal major diameter for all classes except classes 5C and 6C. 0040 .020 . thread. XII. all classes All external threads Internal thread Tolerance on minor dium.0333 .0107 . p.020 . 003» . shall equal or be less than the pitch-diameter allowance on the external thread. The minimum pitch diameter of the internal thread is basic for all classes and equal to the basic major diameter minus the basic depth of thread.0020 . 0107 .0125 . 0.0100 .0058 .0007 .0250 .004» . • Values are 0.0125 .0021 .020 . 0.0100 . 0.0013 . 0028 .0020 .0011 .020 . 7 in. 0250 .0333 .020 in.0030 .0013 . 0025 .0041 .0020V7> 0.0050 .0250 .0010V75 0.—The maximum angular play of a centralizing internal thread. 0250 .0100 .010 . •> Intermediate pitches take the values of the next coarser pitch listed.0037 .(«1 .020 . Basit thread height. The minimum minor diameter of the general purpose internal thread is basic. a class 3C external thread can be used interchangeably with classes 3C or 4C internal threads. 0078 0.020 .0107 . External' thread.0035 .010 . 3C. Acme thread series (max major diameter of external ttw"1 D. which has a larger pitch diameter allowance than either a class 3C or AC external thread.0014 .0028 .(Kill .0050 .0014 . 001» . The maximum major diameter of all class 5C and 6C external threads is the basic major diameter.020 .0017 . 0032 ..0125 .020 ..020 .020 . They are such as to produce interchangeability and maintain a high grade of product.010 . 0100 0125 .0017 .020 . basic. 0065 .0034 • Values for intermediate diameters should be calculated from the formulas in column headings. 0100 .0013 . 4 The minimum clearance at the major diameter between the internal and external thread is equal to col.' diameter.020 S in.010 .0022 0. for Id tpi and coarser. B >> General purpose Minor diameter.0007 . B.0043 .0022 .025» . diameter.0024 .010 .0041 .0500 .0107 .020 .020 .0025 .0050 . 004« .020 .0009 . Classes 5C and 6C external and internal threads can be used interchangeably.020 .0333 .010 .0125 .010 .0016 . 01170 .0125 .010 .01115 .0018 .2-i « in.020 . BASIC DIAMETERS.020 .0022 6.0250 8 in.020 . 0010 .0250 .020 . for finer pitches. /i=0. .) Allowances from basic major and minor diameters.0035 V7> 0.020 . 0055 .005 in.0017 .lp 0. (XI70 .020 »« 1M m 1H-.0050 . thread.0012 .0015 . mwi .010 in. 5.—The tolerances specified herein are applicable to lengths of engagement not exceeding twice the nominal major diameter.020 .0018 .0014 .0022 . 0031) 0.0033 .01)28 . can be used interchangeably with classes 20.0012 . 13 in.op.020 .000» . 0.0045 H H H l « S S 5 4 4 4 4 3 3 3 2 2 2 2 2 .001« . 1.All classes of general purpose external and internal threads may be used interchangeably.5 X pitclwliamcter tolerance.0058 .020 . 2.0012 .003» .010 .0000 .0026 .0050 .020 .0061 . 0.0032 . 0240 9 i».0033 .0050 .—Tolerances and allowances (minimum clearances) for major and minor diameters. plus 0.0011 .0500 Ö. ll. The basic minor diameter is equal to the basic major diameter minus twice the basic thread depth.4.0012 . 001« .0078 0.0024 . on Its external thread for the maximum major diameter clearance is 1° or less.0211 .002« . • The minimum clearance at the minor diameter between the centralizing internal aixl external thread is the sum of the values in eo!s.020 .- M 7 M A» — 16 14 12 12 10 8 6 Ö.0001 .lp above basic.) .0035VT> 10 in.0250 . but only a class 4C internal thread can be used with a class 4C external thread.0043 . plus on internal.020 .. 11 in.025^1) from the nominal diameter. 01)3(1 .001« .020 .0021 . 0050 .lläp Internal thread • External and External Internal External Internal Internal thread.0110» . and 0.0250 .020 .020 . TOLERANCES.02(1 .020 .0033 .020 .0107 . l« 2 2M 2H—2M 3 3M 4 4M 8 .020 .05p» Tolerance on major diameter.0042 .0030 .0035 .010 . !.020 .0100 .0100 .020 .0050 .0021 . D.' plus plus plus « O. 0057 . are given in table XII. 4. Minor diameter External thread internal thread Tolerances on major and minor diameters of external and infernal threads Major diameter Type of thread External thread 0. M« M« 3 in. 3.0012 .0085 . and the sum of the tolerances on external and internal threads. pitch. 0. 3C.0035 Vw | 0.0080 . that the length of engagement exceeds two diameters. (e) The tolerances on the major and minor diameters of the external and internal threads are listed in table XII. the allowance for the ring gage stated in column 5 should be increased proportionately.0080 .0052 . For centralizing fits.0005/0 in. 013» . 0 M« M« M».05p »(Min0.SXpitch diameter toler.4 and XII.0056 .0020 .0037 .0018 . However.5.0095 . and when "go" thread ring gages of these lengths are to be used. (b) The tolerances on diameters of the internal threads shall be applied plus from the minimum sizes to above the minimum sizes. (d) The pitch-diameter tolerances (which control thread thickness) for an external or internal thread of a given class are the same. 0.0120 . LIMITS OF SIZE.0064 . and lead deviations not exceeding the values shown at the bottom of that table.005 in. inclusive. The application of these units is illustrated in figure XII. general purpose and centralizing Classes 20. p.ing{Classes 3C and 5C (Classes 4C and 6C 0.0053 .0150 .—Pitch-diameter Nominal size range * allowances for Acme threads Pitch-diameter allowances on external" threads. are given in tables XII.8. 0052 . 0. 0.0120 .0089 .0087 . for finer | ance | 0.0020VÖ • To avoid a complicated formula and still provide an adequate tolerance.—Allowances applied to the pitch diameter of the external thread for all classes. and 5 are to be used for any size within the corresponding range shown in columns 1 and 2. This is the minimum pitch diameter allowance that is required to maintain the centralizing fit and minimum end play of 0. for general purpose arid centralizing. »Mo IM« IMo IM« l?i« 191« m 2H --■ ---.05p 0. 5. if methods of gaging the external thread are to be used which will detect angle deviation and cumulative lead deviation.0. 91« >M« >M« »M« 1M« IM« IM« VM191« --- 2 in. table XII 4.0060 .3 be used whenever possible.6. Limits of size for centralizing Acme threads of the preferred series of diameters and pitches are given in tables XII. .0113 .TABLE XII. column 4.004 V* Above To and including 1 in.4.0069 .4 and are based on the following formulas. These pitch diameter allowances arc equal to the sum of the allowance on major diameter. 1.0136 5 in.0049 . (c) The tolerances on diameters of the external threads shall be applied minus from the maximum sizes to below the maximum sizes.0063 .) 1 pitches 0. when the product has a length of engagement greater than the standard length of the thread ring gage as shown in table XII.uoioVfl 10. The pitchdiameter tolerances for the product include lead and angle deviations.0032 . 2C.0140 . and XII.0126 .0047 . Pitch diameter tolerances for all classes and for various practicable combinations of diameter and pitch. columns 10 to 14.0049 . 0.0127 .0024 .0042 .0045 .0040 .0094 . for classes 50 and 60.006« .010 in. for classes 5C and 6C.14.5. 0. column 3.020 in.005 in.9. classes 3 and 5. the pitch factor is used as a base. and 5C.0085 .0040 .008 V/> Classes 30. If the lead deviations in the product are greater than indicated.0091 '/!« 91« 'Me •W. 5.0181 4 in. plus an additional amount of 0.0.0035V# -■ (Mtnll.0075 .ö.) IClass 2C Ontra!i>.) ance 0.05p»(Mln< coarser.002v'Z> in.0028 .0035-/Ö 0. 0. These values are calculated from the mean of columns 1 and 2. and minor diameters are given in table XII.006 V/) Classes 40 and 4C.SXpitch diameter toler. ACME THREADS Limits of size fov general purpose Acme threads of the preferred series of diameters and pitches arc fjiven in table XII. •> An increase of 10 percent in the allowance is recommended for each inch. which are to be used for special threads: 4. m 2H 2H 2H 2% 2H 2H 2% 334 3« 4M W m 3V —.0042 . An increase of 10 percent in the allowance is recommended for each inch.12. general purpose and centralizing. 14. XII. for 10 tpi and ll.!i. 1.0112 .3. (X)79 .10.905 in.0170 .0047 .0075 . The application of these limits is illustrated in figures XII. The relative proportions of the pitch diameter tolerances are: class 2. t 4M iH m • The values in columns 3. («173 . the pitch diameter of the external thread shall be below the tabular maximum pitch diameter of the external thread by an amount sufficient to compensate for the measured deviations.4. It is recommended that the sizes given in table XII.—The formulas for the major. table XII. and classes 4 and 6.7.0037 .0060 .and6C.0098 . or fraction thereof. FORMULAS FOR DIAMETERS.10.0160 .0030 .0024 .0070 . the maximum pitch diameter of the external thread shall be decreased by the amount shown in table XII.0099 . 17.005 in.0015 V- Internal thread o.11 and XII.0057 .0070 . with the minimum tolerance value set at 0.0090 .0085 .0105 . or fraction thereof. column 5. that the length of engagement exceeds two diameters.0105 . 0035 . ALLOWANCES (MINIMUM CLEARANCES). 259 times the pitch diameter tolerance. in. 0. right-hand. 0.1667 in. IM . 0.01732 .0229 .0176 .3333p—0. 2 .0190 16.02121 . 0.0201 .0253 . 3Min. 2%—0. THREAD DESIGNATIONS The following abbreviations are recommended for use on drawings and in specifications.0108 . 0.0324 .0114 Win.0316 . Hi in.0193 .. pitch 0.0364 0. For an intermediate nominal diameter.0127 . 16 14 12 10 8 6 5 4 3 24 . No«.0217 5. in. pitch 0.0142 .0280 .0247 in.0262 . Examples of designations: Right-hand Acme threads: ACME—2G=General purpose class 1% 1 I _ 1 • 1* A « */ ' 2G Acme threads. right-hand. —Pitch diameter tolerances for Acme screw threads classes SG and 2C Pitch diameter tolerances for nominal diameters of:» Threads Pitch per increment. in.4p—0.0126 ..00300 0.0079» 0. in..0302 0. inch.00367 0..00704 0. 2 Hi 1W 1 in..6.0155 . 0.01732 . j 1H 1 Diameter increment.0307 . in. major diameter 2% in.01342 .00671 Pitch diameter tolerances for nominal diameters of: • IWin..0190 .C0636 0.0357 . in.00735 0.02449 . 0.6667L— ACME—5C=C e n tralizing class 5C Acme threads.8 in.0147 . 2!4 in.00335 0..0148 Win.00802 . in.00949 0. in. lin. lead 0.0434 Diameter increment.0174 Win.0263 . 0. nominal major diameter 2xk in.02598 . 3 in.0270 .00397 0.0132 .4 in.0219 . pitch 0.01225 .0137 ..0310 .00949 . lead 0. 2« in.0317 . Left-hand Acme threads: J ACME—2G—LH 2%—0.2500 in. 4 3 2M .006 JT) 0.0285 .0387 ..0254 .0140 . 2%—0.0139 .0179 .0143 .. 0.0123 . right-hand.0134 .0229 . in.0294 .0191 . 1W in.4605 in.0194 in.00750 .0168 ..0214 .0170 .0109 . pitch 0.0180 .. (basic major diameter 2. right-hand. TABLE l%~6 ACME—4C=Centralizing class 4C Acme threads.00600 0.0105 Me in.01061 .0128 .0297 0.0122 . 0.0207 . 0.0245 . in.00995 0.4p—0.0185 .03000 Min..0112 . lHin. in..0173 .8L—ACME—3G=General purpose class 3G Acme threads.0117 .8L— ACME—3C=Centralizing class 3C Acme threads.0312 0.03000 0.0117 .030 Vl/» n in.. 14 12 10.0174 .0289 .. 5 in.0147 .0372 .6667 in.0182 .0275 .0154 ?iin.00520 0.0205 .0379 . pitch 0. major diameter 1% in.01061 . 0.0249 .8L—ACME—3C—LH 2&—0.0372 . in. 0.0166 . 0.01342 « The equivalent tolerance on thread thickness is 0. 0..02449 .0158 .00750 .0223 . 0..—The pitch diameter tolerances shown equal the sum of the pitch increment and the diameter Increment .0307 0.0258 .0240 . G=general purpose. HMta. 0151 .0268 .6667L—ACME—5C.0239 in. major diameter 1% in.0224 .01122 0. 2 in.0332 .0277 .8L—ACME—3G—LH IK—6 ACME—IC—LH 27/8—0. 6 . 4 in. and on tools and gages: ACME=Acme threads. 0. LH=left-hand.0212 ...0132 Ji« in.02598 .02121 . double.0302 .01342 .030 Vl/n n in.0084« 0..01273 0.0136 .01500 . in.0394 . in.0220 in.01500 .006 Vx>. single. 8.01200 0.6.0158 .00474 0.). 0.0129 .01897 .0420 0. 2« in. in.0293 . 0.0202 . inch.00866 .0162 .0380 . C=centralizing. double..00561 0..0154 .00946 ..-LH XII. apply the pitch diameter tolerance for the next larger nominal diameter given in this table.0339 .0208 .0300 .0186 .0123 ..3333 in. in. Threads Pitch per increment.0346 .01897 .4 in. 0.0285 .0162 .0165 .00866 . lead 0.0214 in. major diameter 2% in. in.01225 .0427 0.0120 .0115 .0150 .00900 0.0324 .0412 0.00424 0. right-hand. 0.0273 . 2%—OAp—0. double.00802 .0305 . single.3333p—0.0349 .0196 .0235 .0135 Win. lHin.8 in.4p—0. .01039 0. 0116 . in.0083 .00443 .0126 . classes 3G.0059 . i Diameter increment.00594 0.0103 0. in. 0. in.0140 . Wi in.0122 .0094 .00171 0.00990 .7.0058 .0118 .0133 .00101 .00572 .0061 Jf« in.0076 .00343 0.00626 » The equivalent tolerance on thread thickness is 0.0085 . For on intermediate nominal diameter.00350 . in. in. in.00404 . 0135 . 3 in.00700 .0099 .0062 . Win. 0.0133 .00700 .00140 0.0074 .00185 0.0100 IH in.0184 .00198 0.00350 .0049 M« in.00328 0.0051 .00374 . in.0141 .0199 0.0143 .0081 Jsin. in.01212 .0053 Hin.00242 0.0148 .0082 .00297 0.0028 Vß~ Pitch Threads per increment. 0065 . in.0101 16 14 12 10 8 6 5 4 3 a ms.00495 .00990 . i'iUh diameter tolerances for Acme screw threads. 0057 .0088 .01400 0.0091 »«in.259 times the pitcli diameter tolerance.0068 .—The pitch diameter tolerances shown equal the sum of the pitch increment and the diameter increment.0070 . 16 14 12 10 8 6 5 4 3 0.00626 .0145 . 2 in.0143 0.0192 0.0170 0.0167 .5C Pitch diameter tolerances (or nominal diameters of: • Mln.00262 ■ 0. 44 In..ÖÖ72* . 8 .00626 . in. in.0126 . inch.00495 . in.0170 .0107 .014 v'l/'i n in.0155 .0081 .0067 .0163 .0078 . 3C. 0068 . in.00560 0.0060 . 0. H in.001» .00396 0. in. 0064 . .00885 .00524 0.0177 .01143 .0097 .0118 .OOKVZL 0. 0137 . 2W 2 IM m i Diameter increment.0115 0.0151 .0095 .0177 .. 0137 . 0 0054 . in. 2'i in.0104 0112 . 0.0090 .0120 . NOTE.00885 .00157 0. 0.0128 .0196 0.0042C 0.014 Vv» n in. 1 4 in.0063 Hin.0162 .:.0079 .00464 0.0092 . in. 5 in.00808 .0125 .0076 . in.0127 .01400 XII.0147 . apply the pitch diameter tolerance for the next larger nominal diameter given in this tahlc. Ö7ÖÖ7Ö"" .TABLE Threads Pitch per increment. Ö.0145 0. 0.0089 lin.0072 .0062 . in. and .00443 . 01143 . in.0074 .0158 . in.0070 . 0058 .0087 .0069 in.0203 2H 2 m 1W.0077 .00572 . 0174 .0065 . . O.0055 . 0.0097 . 0131 .00443 0. inch.0151 . 0.01212 .0052 .0066 .0086 .00485 0. 0. Hi in.0139 0.0072 H in.0123 .00313 Pitch diameter tolerances for nominal diameters of 1« in.00808 .00221 0.00280 0.0100 0107 .0064 .0174 .0129 . 0. 3» in. n 0057 .00374 .0091 .0094 .0104 .0081 .0181 .0084 . 2H in.0141 0. 0.0102 0110 . in.00370 0. in.00H9 .0114 . 00408 .0049 . 0.00400 0.0098 .0038 % in.0069 . 214 in.0108 .00408 .0090 0.0126 .0039 . 16 14 12 to. In. 1W 1 . in.0065 ..00200 0. 0.0071 .0046 .0060 .00316 . in.0048 .0089 . in.0050 Hin. in.0041 j %6 in.0103 .00707 .0041 .00632 .0046 . in. 3V4in. . in.0068 .00300 0.0111 .0055 .0121 Diameter increment.0.0058 Hin. in. 0.0054 .00158 0.00332 0.00245 0.00354 . classt s 4G.0095 .0041 . 4C.0064 . in. 0106 .00f?. 0. 0.0049 .0067 .259 times the pitch diameter tolerance.00224 Pitch Threads increment. 5 in. 2 .00265 0. 007*1 .00289 .00235 0. in.00122 0.0145 3 2M-.0083 .0104 Ö.0043 . 5 4 3 2H 2 IM 1 Us i Diameter increment.010 Vl/n n in.0115 .00447 .0038 . For an intermediate nominal diameter.0044 .0098 ..0086 .16 .0113 .0059 .00577 .0071 1!4 in.0050 .0072 16 12 10 8 6 .0045 0017 . 0075 .00577 . m in.01000 . in. per Inch. .0062 . 2M in.0092 .0042 .00187 0.0087 . .00267 . NOTE.0039 .00MS6 .00500 .0064 .0108 .002y7>. 0.TABLE TMtch Threads per increment. in.Ö047 .0050 . in. 0.00283 0.0080 . in.009« .0076 .0142 0.00100 0.008:6 . 0.010 VVn n in.0063 lin.00447 . 10 8 . 0.00866 .00816 . 3 in.0066 .0073 0.8 — itck diameter tolerances for A cme screw threads.00632 .00424 0.0042 .0084 .0082 . IH in. 0.0035 Me in. lHin.00374 0. in.0073 .00212 0.0063 .00132 0.00316 0.00707 .0074 0. in.00354 .0093 .0052 .0041 .00447 » The equivalent tolerance on thread thickness is 0.ÖÖ85 . 0.0127 .0058 .0088 .0042 .0078 . 4 in. 2 in.00112 0.0101 . 0. inch. in. Pitch diameter tolorunu'« for nominal diameters of: ■ lHin.0053 .0100 .Ol'JOO a XII.0099 Ö.0060 . Ö.0058 .0057 .0131 . in.0069 .0101 6 5 4 0.0036 .0095 .0061 . 0.0091 .0102 0.11045 Win.0140 0.00250 . in. 0. 4M in.00173 0.0105 1M-.0122 . in. Ö.0051 ¥i in. 0.0051 .Ö045 .0137 0. in. in.0129 .0054 .00267 .002 V#— 0. apply the pitch diameter tolerance for the next larger nominal diameter given in this table.00250 .00141 0.00316 .0037 . 0.—The pitch diameter tolerances shown equal the sum of the pitch increment and the diameter increment.00346 0.0065 lHin. 0.0124 .0119 0124 .0090 .0076 .0040 .00500 . and 6C Pitch diameter tolerances for nominal diameters of: • }i in.0067 ..00289 .0062 .0055 .0056 .0102 ...0053 . 0. 4) shall be applied minus.0003 in. XII.—(a) .6. 0.4.0001 in. shall be added to the above values.—The variation in lead of all Acme thread gages for classes 3. columns 3 to 5. This insures that the bisector of the included angle will be perpendicular to the axis of the thread within proper limits. 10 1.10. 30.0006 in. col. 4G.7 or XII. or 5 4 Ext max pitch dia. the minor diameter of the "go" thread ring gage shall be less than the minunum minor diameter of the internal thread by the amount of the allowance on pitch diameter.—The major diameter of the basic-crest maximum-metal limit thread setting GAGE. "Go" THREAD RING OR THREAD SNAP Major diameter. or tables XII. (b) GAGES FOR EXTERNAL THREADS l 2 EXTERNAL THREADS 3 Major dla: Basic (max)« Min Pitch dia: Max Min D fl(«D-0.010 in. TOLERANCES ON MAJOR AND MINOR DIAMETERS.—The pitch diameter tolerances for gages for classes 2G and 2C external and internal threads are given in table XII. 6C 2. The tolerance (table XII. TOLERANCES ON ANGLE OF THREAD. (c) Minor diameter. and plus 0.5. for 10 tpi and coarser. are necessary for the proper inspection of Acme threads.8 B+allow from table XII. TOLERANCES ON LEAD. and 6C external and internal threads in table XII. cols 3 or 4.7 or XH.5X pitch dia tol from tables XII. cols 3. or gages for class 2 product.8 XII. table XII.4.TABLE XII. 30.—The major and minor diameter tolerances for Acme thread gages are given in table XII. (d) Length—The length of the "go" thread ring or thread snap gage should approximate the length of engagement (see footnote to table XII. col 7 table XII. or slight projections on the thread form. cols 12 or 14 Pitch dia: Basic (min) = Max B-0. 5.7. or 0.7. col 3 Ext max minor dia-1.0002 inch between any two threads not farther apart than one inch. XII. than the maximum major diameter of the external thread.8 B—p—allow from table XII. from table XII.8 D—p—allow from table XII. cols 4 or 5 Int min major dia+tol from table XII.—For general purpose external threads.—The pitch diameter shall fit the maximum-metal limit thread setting plug g«ige. col 5 Int min major dia+tol from table XII.14. The equivalent deviation from the true thread form caused by such irregularities as convex or concave sides of thread. 13. 13.Sp Int min pitch dia+tol from tables XII. 4C. and 6 product shall not exceed 0. for the various pitches are tolerances on one-half the included angle. 40 Classes 2C. the cumulative error in lead shall not exceed 0. For centralizing external threads.—The major diameter of the "go" thread ring or thread snap gage shall clear a diameter greater bv 0. Acme thread clauses Classes 2C). as specified in table XII..005 in. 3C.5. or adequate gaging instruments for thread elements.Basic diameter (for classes 5C and 6C) p-Pitch 7.5p Int min pitch dia+tol from tau« Xil. However.6.. The dimensions of "go" and "not go" gages should be in accordance with the principles: (a) that the maximum-metal limit or "go" gage should check simultaneously as many elements as possible. for pitches finer than 10 tpi. 3. and that a minimum-metal limit or "not go" thread gage can effectively check but one element. or 0. cols 8. 3.13. GAGES FOR ACME THREADS Gages representing both product limits. or XII.025 V5) B-tolfrom tableXII.— (a) Major diameter. 2. inclusive. should not exceed the tolerances permitted on angle of thread. 13. inclusive. column 2.13. inclusive.4. and for gages for classes 3G.7. to allow for possible deviations in concentricity of the pitch and minor diameters of the product. (a) GAGE TOLERANCES Tolerances for the thread elements of "go" and "not go" thread gages for Acme threads are as specified below. or XII. for figes with a length over 5 to 10 in. for gages with a length over 3 to 5 in.—The tolerances on angle of thread. fl-p+O.. for gages with a length over 1 to 3 in.12. 5C. col.R Minor dia: Max Min INTERNAL THREADS Major dia: Min Max D+allow from table XII.4.lp 40) D-p+O. column 4.4. 11. 4. 3C.4. XII. 4C) Int min minor dia+tol from Int min minor dia+tol from table XII. (6) Pitch diameter. cols 9. 4.SX pitch dia tol from tables XII. 3C. column 3. and (6) that permissible variations in the gages be kept within the extreme product limits.5. For multiple threads.8 Minor dia: Basic Min Max D-p B-p D-p (for classes 20. 1.4. col 7 D—Nominal size or diameter. or 14 fl-O.5.0004 in.4.9 —Formulas for diameters. The tolerance shall be applied minus. 14) but should not exceed the length specified in table XII. B. 4C Classes 5C. MAXIMUM-METAL LIMIT THREAD SETTING PLUG FOR "GO" THREAD RING OR SNAP GAGES. col 3 Ext max minor dia-l. column 5. the cumulative tolerance for pitch and lead shall be multiplied by 1.4. TOLERANCES ON PITCH DIAMETER.6. 10.lp (for classes 2C. cols B-tol from table XII.7 or XII.tol from Ext max pitch dia—tol from tables XII.01 in. or 13 11 or 13 Int min pitch dia—allow Int min pitch dia-allow from table XII.4. the minor diameter of the "go" thread ring gage shall be the same as the maximum minor diameter of the external thread plus 0. g SSe* SSE. saj ag_.^ * » ISi ■m 22? SSS i. Bö^ ag_. a Ö X •1 •o OS W E nC ol I a ü if a Z S5 36 cl IE c liJU 650170« pH 11 .S_5_K llflj O i fi fi « i 8 * •a Jits I c.-S|§ *-§§§ 8281 sis ?K8 |§ weäS § m Soooocc ill is ssl |SS 635© oSc oc 5 !§ ill 88© 88s II! |S3 £33© el II ill it §r»eg S8S Q»22 111 883 art« |*«22 cS ■MS issi izs 31 e c tilg «eo ran 11? ro ill 5* sä !l §Si S£i g« •'S ill cocoo coco© fig c £338 .888 COCO ' n co 111 ?S?8 8SS 5'2*° go© IPS « WO Iss e s ■SSSS 95 sis 8S£ NO* i-r-o £f5c c4ej i sis -is 5N 82 5CN35 eoeococo (OtC t-CO •*©C*)CO «sS 528 K2Sf CO COS SAO 588 CO coo «CO© eo©co CO"5N ©—© 2S5S 00 00 CO 01 Sis 6SS iss gss ooofio 5S8 ss? ssss 23? ■a I>CO"»> t-r-o ccoo© S8S «38 i-*r»o 238 e 5oö2 3£S S?8R PS S5S?S sss MNO coeoo CO coo I •i — CO coo *§p . i a = !S_.SSH SSe.ess weo^p» «nag |S8 5 cöo n a! ••in X m J < gss ill pi cocoo cocoo m lit «wc ?SN nSu ISS i?8S J»8 SS 9 aooa SS8 1S1 SS8 c*Ho s 588 g=3a c3?i© 5Sc III SSH ■32 L.S3 RKC s§ SHe |S8 SSS ift«ft *<*■«" g«<D •tft'«« g2S §23 5.SS oaei las «si IIS <S© ssss ss?s 111 CO Oft W CO 80 CO IS? S| {8 g^2 to e5S3e cjwwjj K CO «A CD .geriete ^. 14.—The pitch diameter of the maximum-metal limit thread setting plug for all external threads shall be the same as the maximum pitch diameter of the external thread. tolerances. column 4.14. classes 2G. The class Z tolerances given in footnote of table XII. the pitch diameter of the maximum-metal limit thread setting plug shall be less than the maximum pitch diameter of the external thread by the amount stated in table XII. "Go" PLAIN RING OR SNAP GAGE FOR MAJOR DIAMETER. 3. 4) shall be applied minus. SG. col. "NOT GO" THREAD RING OR THREAD .INTERNAL THREAD (NUT) 0.—The diameter of the "go" plain ring gage.13 shall be applicable to gages for centralizing threads. 2 and 3) shall be 12 applied minus. (d) Len(ßh. if the product length of engagement exceeds the length of the ring gage. column 5. NOTATION plug gage shall be the same as the maximum major diameter of the external thread.—The length of the maximum-metal limit thread setting plug gage should approximate the length of the "go" thread ring or thread snap gage.—Illustration of allowances. (b) Pitch diameter. 4. and crest clearances. The major diameter of the truncated maximummetal limit thread setting plug gage shall be smaller by one-third of the basic thread depth (=p/6) than the maximum major diameter of the external thread. (c) Minor diameter. table XII. 4) shall be applied plus. or gaging dimension of the "go" plain snap gage.—The minor diameter shall be cleared below the minimum minor diameter of the "go" thread ring gage. shall be applicable to gages for general purpose threads. column 3. Heavy Hoes show basic sice. and 4G.13. k~l»isic thread height. The gage tolerance (table XH.13.0945>> MAX EXTERNAL FIGURE THREAD (SCREW) XII. The gage tolerance (table XII. general "purpose Acme threads. The tolerances shall be applied minus. p-pltch. The gage tolerance (table XII. col. col. shall be the same as the maximum major diameter of the external thread.13. Tolerances given in table XII.13.3. However. © fl 38 MMMM C©OM T © 8S§ MM _ t © a**« M©M MM' M M 5M© mi-X W —© MNO MM C")«! "T M — ••*■*•»© M ci i.be*-© i-*-Q ?g si gg gg 83 3g MC 5=3= l§§S |3i ? M X» »MS* s. S2. 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MO g«nt-cD XXXCÄ —— — ÖKS8S 2g3 3SS RS38 i.*T M MM t-©0C CM© MOM MM — MM ^r i.— T X»»'-»' OMI- m«T— —MX M""'* fjl-m 5> O *© MM ©t*M— ©?5r9 ©OCX I.- ~ ..r©©© SM© MM' m© © M M* M — X «30 MM© M'C4* 5 »o © .8 £8 $2 sg S2S5 §SS gSS B%£ .£- ^ •s 5 «-.© — -o © t.M SS o© © — »I© x 25N »Sfis **■■<#** ©M© — t> ■*> I* CO MOM **FMM caw l-l-O MM-* »^"* S d» *«I— I— c ?i gffi SS 883 §55 gg3 g£i S—* 9 55 35© — 3*<D" CO OS «5 "5«5 O -»•>■** 35I-M t 35XM . .X O —©OO g^2* ^ != © ©■©© ©xfi *¥ — M MM© i-«»* © .© — © *.— T< ©-»■(- i-x— ID?« t-mx "©^S £tD »M MM M© ©o MX ^o ©o ©©MM xm©i<*.=3 t M — 35 "?M ift^fi 35 © ©■"»■ MM 35 O ©in in B5i-M MM© ©MM 35t-M MMÖ ©»»"■* 35j5© MMC ©v* 35MtMM© SI" B5M wjw XM i-O M © ©mm *MM 35 © — — — © ©O© QMM 351.8 **3 SS "T O t-O SS *# © I"© x— "f O h-O 5X(ÄC9 »Sr« I^M>O ujmo SB.© 38 = © I.Sä SS SS £S iSSS SSS S!:S ftSS c^ §oo l-M S 99 S2 SS2 ^SS Ergg ^1:5 « el S3 Si^S SS= SiS R£S K i5g Kg lag llo SSS IES X «5 ci « (C* ©o *M M© s 6 8 Sg Sg SS SSS3 SSS SSS SSg MX XM rt— M© ©o M© O'W X— — OJ O© M— — © Ml.© © ©Co MM' coo MM' ce.3c— 35I-M ©So 5oo 35m© 35m© g 2-8 ©©© 1 e o «a 2g gg «g gßsi sis sss is! lg gg so i-f-i-ixxo 5b a Ss as sss ss= s§g ss S 3S SS g|S S Sg gS oo jS3 32S ill «Si Ü3S SSs 8 C .O I.*9.<5«5 UHM ?i^H «50 ««o »».M — 'M *' M O ©MM OO© 35 35 — " MM© . fi io cct-O . ggg : S ! : i ! 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(J 13 ■o 1 a O S f E d B a 3 X3 r d u o u Ü o 14 .o 3K8 388 O "3 NNO» MM I ■a o .on —■ »«« «So 3 * PS PS ?XS §8= ISS jc-l w t-r-o POPS na «53 W W M w cow. i S9I 06 W- a si 11 Hi §sl 9s§ *«° StS £*^3 2§ S$»© S»88 S8s ©Q© uM- 'S 88 .8 £8 £8 e o 8 3 8 SRs N S N S p« 8| §88 8S| 3£jj i-a6© 003o o QOoOc $060 '5 'S•2 S is 38 E<co eis: P-K© SK8 l-r-2 38 SS2 Si 2 SSS S§S 8 SÜ SSS 5S8 S3S8 3 X :«3 5 S?5S © 1 s e •8 B •a S3 o 38 ts ass ass ass 88 8S8 338 338 < «' i i i i i i i i : i i i i i i i i I i i i i i i :i i sS£s£sssss£ss£ a gg gg gag sag. When a multiple thread is involved.INTERNAL THREAD (NUT) 0.—The pitch diameter shall fit the minimum-metal limit thread setting plug gage. If the value for minimum minor diameter determined by the formula is greater than the minimum pitch diameter of the external thread. col. Heavy lines show basic size.01 in. centralizing Acme threads.435p maximum width between intersections with the flanks of the thread.067P MAX 0. and 4C.—The minor diameter shall be the basic minor diameter of the internal thread plus p/4. NOTATION p=pitch t=busic thread height. SNAP GAGE. SC. (c) Minor diameter.0707p MIN ~"^/' 4 BASIC THICKNESS OF THREAD t=0.—(a) Major diameter.050P MIN 45«—-"* ct DETAIL OF CHAMFER 5* EXTERNAL THREAD (SCREW) FIGURE XII. (6) Pitch diameter. the minimum minor diameter of the gage shall be specified as the minimum pitch diameter of the external thread. 5. 4) applied plus.4.0945P MAX 0. than the maximum major diameter of the external thread.—The major diameter of the "not go" thread ring or thread snap gage shall clear a diameter greater by 0. tolerances. THREAD SETTING PLUG FOR "NOT GO" 15 .13. classes SC. (rf) Length—The length of the "not go" thread ring or thread snap gage should approximate 3 pitches (see footnote to table XII. the "not go" thread ring or snap gage shall be of such length as to provide at least 1 full turn of thread. 14). The clearance cut may have 0. and crest clearances.5p M^ i 0. with the tolerance (table XII.—Illustration of allowances. and crest clearances. The gage tolerance (table XII. (d) Length.07p MIN EXTERNAL FIGURE THREAD (SCREW) NOTATION XII. centralizing Acme threads. p=pitch »»basic thread rend height Heavy lines show basic form.5. (c) Minor diameter. (6) Pitch diameter.—The minor diameter shall be cleared below the minimum minor diameter of the "not go" thread ring gage. The major diameter of the truncated minimummetal limit thread setting plug gage shall be truncated one-third basic thread depth (=p/6) smaller than the maximum major diameter of the THREAD RING external thread.—Illustration of allowances. 4) shall be applied minus. col. col.13. OR THREAD SNAP GAGE.13. classes SC and 6C.—The major diameter of the basiccrest minimum-metal limit thread setting plug gage shall be the same as the maximum major diameter of the external thread. The gage tolerance (table XII. VI Q «4 5 EC 4 o 1 o «I Ui rv Uj \ f ILL ET R/OIUS O. 4) shall be applied plus.INTERNAL THREAD (NUT) * Ui O ■^ U) u £ Q: it <* o ^ cs *5 jt (fc <* a.—The pitch diameter shall be the same as the minimum pitch diameter of the external thread. with the tolerance applied plus.—The length shall be at least equal 16 . tolerances.—(a) Major diameter.IOP MAX 0. 5 4 3 In. 3 above.0007 in length over 3 to 6 in. wherever they may be utilized successfully.0010 in length over 6 to 10 in. is the length if engagement.510 NOTE.'. col.00020 .002 .002 .0011 . .80~(l.010 in.13. 2 and 3) applied plus.0039 Nominal major diameter of external thread Length of "go" ring gage Above To and including XII.002 . Acme threads Tolerance on pitch * diameter Maximum amount 2 diameters length of engagement exceeds length of gage Threads per inch » Classes 20 and 2C Classes 30. Should a "go" gage shorter than the length of engagement be chosen. 0.0003 In length of ^4 in.-—(a) Major diameter. p.—The above compensation is based on a length of engagement nol exceeding two diameters and a lead deviation in the product not exceeding the following values (in inch): 0. Oage Itlanks. 14. 5C. if the lead deviation in the length of engagement. and 6C 3 Tolerance • on major and minor diameters Tolerance on half angle of thread 0 1 1 in. Af. as listed in the latest issue of CS8.002 .0015 .0010 . 2 in.002 .0018 . 0 0.0006 . so determined.0008 .—The length of the "go" thread plug gage should approximate the length of engagement (sec footnote to table XII. in.0008 . as follows: Size range Class Z tolerance Above To and including in. Is the length of the gage and /.0015 .002 .005 in. to allow for possible deviations in concentricity of the pitch and major diameters of the product. where O is the product pitch diameter allowance. GENERAL PURPOSE THREADS. and for "go" and "not go" plain ring or snap gages for major diameter of centralizing external threads. for pitches finer than 10 tpi. 4C.0015 . {d) Length.0021 »Intermediate pitches take the tolerances of the next coarser pitch listed in the table.0007 . the allowance is sometimes increased a fixed amount. Alternatively.—The major diameter of the "go" thread plug gage for centralizing threads shall be the same as the minimum TABLE XII.0010 . "NOT Go" PLAIN SNAP GAGE FOR MAJOR DIAMETER. For reasons of economy or limitations in gage manufacture or use.00010 .0019 .. 0 1 2 4 5 Hi i% min 10 10 10 10 8 8 8 8 0 6 6 5 5 5 n* 2 diameters.00025 in. 2. This arbitrarily reduces the tolerance on diameter.0004 in length over H to Hi in. When instruments are used for checking diameter it is a imple matter to make this allowance. "Go" THREAD PLUG GAGE. 0. 1 1W 14 m m m 2 3 4 in. 3C.13 shall be applicable to gages for centralizing threads.002 . 17 .0009 .002 . (c) GAGES FOR INTERNAL THREADS THREAD PLUG GAOE. 7(a) 3. >> These pitch diameter tolerances for thread Qaqts are not cumulative.0008 .. or less.0007 . column 4.0006 .00012 . for 10 tpi and coarser. 0. TABLE (b) Pitch diameter.0010 .0012 . (2) Avoid too cumbersome ring gages as well as excessively expensive gages by limiting the length of "go" thread ring gages to maximum lengths given in col. shall be applicable to gages for general purpose threads. The maximum metal condition must be reduced to assure free assembly of product. of course. independent means should be used to measure lead deviation in product. thread ring. When thread plug and ring gages c used.0019 .0013 .001 .13.0027 .0014 in.0015 .510 4.002 .0019 .—The pitch diameter shall be equal to the minimum (basic) pitch diameter of the internal thread with the tolerance (table XII.—Pitch diameter compensation for adjusted lengths of "go" ring gages fo) geneial purpose and centralizing threads Maximum amount pitch diameter of "go" ring shall be less than maximum pitch diameter of external thread 5 in.0018 .259O.825 1. than the minimum minor diameter of the internal thread. and "not go" gages should IK' three pitches long. The principles have been established in the foregoing requirements that "go" gages should approximate the length of engagement.0005 . CENTRALIZING THREADS.0019 .01 in. (c) Minor diameter.—(a) Major diameter. plus on internal thread) accordingly Is: Ai'=3.510 2. Class Z tolerances given in footnote of table XII.-—The minor diameter shall clear a diameter less by 0.0008 .510 in. and minus 0.0010 .0019 . thus permitting the use of standard or moderate length thread plug. .001 .—Tolerances for "go" and "not go" thread and plain gages.13.825 1. particularly where long engagements are involved.00016 . The gage tolerance shall be applied plus.0006 . they do not include tolerances on load and on half angle.. The required amount of change in pitch diameter.^') Jp.002 .029 0. that is.—The gaging dimension of the "not go" plain snap gage shall be the same as the minimum major diameter of the external thread.002 0 0 0 0 0 0 0 0 0 0 0 0 0 0 m \U 2 2'i 214 2?i 3 4 .0005 in length over H4 to 3 In. 14) but shall not exceed twice the nominal major diameter unless specifically requested.0007 . ± 24 254 2H 3 4 5 2 2 2» 3 3 5 7 m 2M 2 IM IV* l - . 2in 2in 2 in 2Ü1 2 In 2ln 2*4 in 214 in 2Win 3 in 3 in :tin M 1 % H <teg 16 14 12 10 8 6. 4) shall be applied plus. col.13. 0... 10.0005 . 0.001 . . .0010 in. 6.—The major 1. Tolerances given in table XII.01X16 . (4) Take full advantage of modern equipment for producing and checking accurate leads.0012 .. as outlined ti he above table.510 6. instruments might be used for checking diameters and angles independently. For these gages the tolerances are class Z.0009 . Lead tolerances are given in par.to the length of the "not go" thread ring or thread snap gage. or thread snap gages. • These tolerances are applicable to all gages except the "go" and "not go" thread plug gages for major diameter of all classes of centralizing internal threads. The gage tolerance (table XII. 40. of tlie product (minus on external thread. (3) Avoid excessively cumbersome thread plug gages by limiting maximum length to two diameters wherever possibk'.0006 . exceeds 0.510 2 510 4. it may be desirable to modify these principles to: (1) Take advantage of the economies of using standard blanks. 0. where /. "Go" diameter of the "go" thread plug gage for general purpose threads shall be equal to the minimum major diameter of the internal thread minus 0. 4) applied minus.14).14). Both corners at the crest shall be chamfered equally at an angle of 45°. 13). with the tolerance (table XII. SECTION XIII.00. {d) Length—The length of the "not go" thread plug gage should approximate 3 pitches (see footnote to table XII. (d) CONCENTRICITY Methods of securing concentricity between major and pitch diameters of external or internal threads must be determined for each individual application.01 in.375p.13. Modified Form 1 Stub Acme 0. 3. The gage length shr. When a multiple thread is involved.re now extensively used for a variety of purposes.—The diameter of the "not go" plain plug gage shall be the same as the maximum minor diameter of the internal thread. 1. col. 2. +0.—The basic thickness of the thread at a diameter smaller by the basic height of thread (for which see previous paragraph) than the basic major diameter. New York 18. The crest corners shall be chamfered 45° equally to 'cave a central crest flat not more than 0. 1(c). and length of gage shall be the same as those given in 1(b). (b) Pitch diameter. classes 2C.—The diameter of the "go" plain plug gage shall be the same as the minimum minor diameter of the internal thread. 3t)th St.—(a) Major diameter. and 4C) or the maximum pitch diameter of the class 6C centralizing external thread (for centralizing internal threads. Section XII. The minor diameter shall clear a diameter less by 0. The pitch diameter shall be the maximum pitch diameter of the class 4C centralizing external thread (for centralizing internal threads. "NOT GO" THREAD PLUG GAOE FOR MAJOR DIAMETER OF CENTRALIZING INTERNAL THREAD.435p maximum width between intersections with the flanks of the thread. Its use has been generally confined to those unusual applications where a coarse-pitch thread of shallow depth is required due to mechanical or metallurgical considerations. regular Acme threads were intended to replace square threads and a variety of threads of other forms used chiefly for the purpose of producing traversing motions on machines. 2. 5.13. ANGLE OF THREAD. The latest revision should be consulted when referring to this ASA document.. leaving a width of flat at crest of 0.13). Acme threads r. footnote of table XII.—The major diameter of the "not go" thread plug gage shall be equal to the maximum (basic) major diameter of the external thread minus p/4. -0. 4. minor diameter.— The pitch diameter. . The length should approximate 3p (see footnote to table XII.—The pitch diameter shall be the same as the maximum pitch diameter of the internal thread. The gage tolerance shall be class Z (footnote of table XII. While threads for valve operation may be made to this standard. The line bisecting this 29° angle shall be perpendicular to the axis of the thread.2Sp. applied plus. tools.Y.— The major diameter shall be equal to the maximum major diameter of the internal thread. 2 and 3) applied minus. col.—The angle between the flanks of the thread measured in an axial plane shall be 29°.3p. with the tolerance (table XII. provides information and data pertaining to the use of the regular standard Acme thread form. 5. with a minus tolerance of twice that given in table XII.13). column 3. the "not go" thread plug gage shall be of such length as to provide at least 1 full turn of the thread. ALLOWANCE (MINIMUM CLEARANCE) AT MAJOR AND MINOR DIAMETERS. 4. and 1(d) above. Gage Blanks.07p. The approximate depth of cnamfer is Q.01 in. 18 6.25p.—The pitch of a thread is the distance.major diameter of the internal thread with a plus tolerance (class Z. The clearance cut may have 0. "NOT GO" THREAD PLUG GAGE FOR PITCH DIAMETER OF ALL INTERNAL THREADS.13. PITCH OF THREAD. than the minimum minor diameter of the internal thread. 3. this application is highly specialized and these data should not be used without consultation with the valve manufacturer.13). GENERAL AND HISTORICAL When formulated prior to 1895. classes 5C and 6C). applied minus.24j/ wide. (c) Minor diameter.ll be in accordance with the latest revision of CS8. between corresponding points on adjacent thread forms.—The basic height of Stub Acme threads shall be as follows: Standard Stub Acme 0. 2» W. The Stub Acme thread came into being early in the 190ö's.02p.—The minor diameter shall clear a diameter less by 0. etc. The gage length shall be in accordance with the latest revision of Commercial Standard CS8. the "not go" gage shall be of such length as to provide at least 1 full turn of thread. measured parallel to its axis. SPECIFICATIONS FOR THE STUB ACME FORM OF THREAD 1. Modified Form 2 Stub Acme 0. The included angle of the thread shall be 29°." which is published by the ASM F. minor diameter. THICKNESS OF THRE\D. STUB ACME THREADS4 1. 3C.5/). The gage tolerance shall be class Z (footnote of table XII. "Stub Acme Screw Threads.. N. HEIGHT OF THREAD. and length. applied minus. than the minimum minor diameter of the internal thread. "NOT Go" PLAIN PLUG FOR MINOR DIAMETER OF INTERNAL THREAD. When a multiple thread is involved. The tolerance shall be class Z (footnote of table XII. p. "Go" PLAIN PLUG GAGE FOR MINOR DIAMETER OF INTERNAL THREAD. shall be 0. (b) Pitch diameter. A minimum diametrical clearance is provided at the minor diameter of all Stub Acme thread assemblies by ' Tills section Is In substantial agreement with American Standards Association publication ASA BIS. . The minimum pitch diameter of the internal thread is basic and equal to the basic major diameter minus the basic height of thread.37. p per inch. 1. The basic minor diameter is the minimum minor diameter of the internal thread and is equal to the basic major diameter minus twice the basic thread height. 19 . ance • 0.22500 . 08571 .03000 .12500 .. 0.controlled.75000 1. The basic thread form is symmetrical and is illustrated in figure XIII.0476 16 14 12 10 8 8 7 6. 1356 .2764 . the tolerances and allowances for general purpose threads shown in tables XII. with the Minimum tolerance value set at 0.1300 . 0057 .300(10 * in.0850 .3 and are based on the following formulas: Major diame Extern«! thread 0. A minimum diametrical clearance at the major diameter is obtained by establishing the minimum major diameter of the internal thread 0.5. 7.020 in.O40M . XII.07143 . This class corresponds to the class 2G (General Purpose) of section XII.28571 .0264 .IC64 .07M3 .MH»«> .25000 . I 0.4224 ! 1 • Allowance Is shown in table XIII. = » + »«0. may be used to determine the limits of size for mating threads. Pitch diameter tolerances are the same as those given in table XII. table XI1I.0475 .4. (Min-o/m".. p.142X6 in.51» . table XI11.2501» .005 In.06250 .02500 .03750 . .4224p 1 2 in..3168 i .3116 .0. and 0. BASIC THREAD FORM DIMENSIONS. .00000 .50000 .2. 0528 | | ' ! 1 0. STANDARD STUB ACME THREAD SERIES There is established herein only one class of thread for general usage.itaio .40000 . 7.12000 . IT tolerance Minor diameter tolerance External throw! l.33333 .3.8.010 in.11111 .08333 .150110 . col.0433 .10000 .1408 1 .03571 . which is recom- » To avoid a complicated formula and still provide an adequate tolerance. ».010 in.ti.3p ^» allowf-P/2 (basic). 0.07143 . (a) Special requirement*. The tolerances on the major and minor diameters of external and internal threads for use with special threads are listed in table XIII.04167 .03125 .—The tolerances specified are such as to assure interchangeability and maintain a high grade of product. mam .0238 .0704 I .115.10000 .2 and not divisible by 1/16 shall show the actual basic major diameter in decimals on drawings. and 0. 02143 . 3. r". I .1.nxpitch diameter tolerance. 0300 . p. 1. 0370 . 6. The tolerances on diameters of internal threads shall be applied plus from the minimum sizes to above the minimum sizes. 2. The pitch-diameter (or thread-thickness) tolerances for the product include lead and angle deviations.0HI3 ! . and tools. The tolerances on diameters of external threads shall be applied minus from the maximum sizes to below tlie maximum sizes. Kim» . TOLERANCES.66667 . 2100 I . LENGTH OF ENGAGEMENT.establishing the maximum minor diameter of external threads 0. 4. 1.2. 3 in.3.2112 . the pitch factor is used as a base. 16687 I . shall have allowances and tolerances in accordance with footnote b. and XII. 2350 ' . 3.WXaliowance • Total Il.06250 . 4 to 9. STANDARD STUB ACME THREADS TABLE XIII.0417 .—The tolerances specified herein are applicable to lengths of engagement not exceeding twice the nominal major diameter.1638 . specifications.'' There has been selected a series of diameters and associated pitches of standard Stub Acme threads listed in table XI11. such as on thinwaHed components.l»5 In.1428« .16667 .1100 .06000 .0845 . above the basic major diameter for 10 tpi and coarser.0400 .05S1 .0652 . (b) Special diameters.08033 . below the basic minor diameter for finer pitches. 1207 .—Special diameters not shown in table XI11.0422 .4172 m .» Internal thread l. 05556 . *' For use only where the major diameter of the Internal thread and the minor diameter of the external thread must IK.20000 . below the basic minor diameter on 10 tpi and coarser. If a fit having less backlash is required.4224p0.6.5.33333 . Pitch-diameter tolerances for various practicable coinI inations of diameter and pitch are given in table XII. pp.—The maximum major diameter of the external thread is the basic (nominal) major diameter. 3.2060 . 1056 .05 p. 5 4 3W 3 2\i 2 IM 0. (Min0. and tabulated tolerances..).-Standard Stub Acme thread form.020 in.20(100 . table XIII. 1251» .01875 .1* Internal thread n.icht height of Thread ("rest of of thread thread. basic dimensions I Threads Pitch. above the basic major diameter for finer pitches.—Applications requiring special machining processes resulting in a basic diameter less than the nominal shown in table XI11.03333 . in order to reduce to a minimum the inventory of both tools and gages.3.6.2. column 1.027« . 0700 . mended as preferred.115 p. Xli.1004 .04285 . These diameters and pitches have been carefully selected to meet the present needs with the fewest number of items.07500 .0352 . 050(10 .20000 .5 .0238 .0302 . 0326 . BASIC DIAMETERS. 05000 . The pitch-diameter (or thread-thickness) tolerances for an external or an internal thread are the same.nation* from nominal diameter.—The basic dimensions of the standard Stub Acme thread form for the most generally used pitches are given in table XIII.n Width of flat at: Hoot of internal thread. thread (basic). IflMI j .4.0529 .311«) in.OXpttch diameter tolerance. 28K'. CLASSIFICATION AND TOLERANCES. XII. 0. thickness internal (basic). crest of internal thread F„-0. if methods of gaging the external thread are to be used that will detect 20 angle deviation and cumulative lead deviation. col.3p« basic height of thread F.-0. or fraction thereof.—Allowances applied to the pitch diameter of the external thread are based on the major diameter and are given in table XIII. ALLOWANCES (MINIMUM CLEARANCES)..259X(minor diameter allowance on external thread) 4.—Standard Stub Acme form of thread. The application of these limits .4. of flat i>.14. 5. However. the maximum pitch diameter of the external thread shall be decreased by the amount shown in table XII. 5 should be increased proportionately. and when "go" thread ring gages of these lengths are to be used.pitch n=number of threads per Inch N-number of turns per inch A =-0.4^4p=0.4224p»=0. 5. that the length of engagement exceeds two diameters. the allowance for the ring gage stated in col.=0.5.-0.259X(major diameter allowance on internal thread) F. col. 14. STANDARD STUB ACME THREADS Limits of size for Stub Acme threads of the preferred series of diameters and pitches are given m table ÄI1I.FIGURE 2a-29° XIII. 3. If the lead deviations in the product are greater than indicated.4224p-baslc width of flat of crest of external thread Fr. 17.. LIMITS OF SIZE. p. the pitch diameter of the thread shall be below the tabular maximum pitch diameter by an amount sufficient to compensate for the measured deviations. and ead deviations not exceeding values shown in the footnote to that table.4224p-baslc width. An increase of 10 percent in the allowance is recommended for each inch.1. NOTATION p. When the product has a length of engagement greater than the standard length of thread ring {jage as shown in table XII. 7.06250 .5000 .5 are based on the following formulas: External Threads (Screws) (Basic) Max major diam=Nominal size or diameter.29000 .16667 . THREAD DESIGNATIONS Standard Stub Acme threads shall be designated as shown below on drawings and in specifications.90000 .90000 .3750 1.90000 .3.0900 2.05000 .7000 .3000 1.1056 . Max minor diam=Int min minor diam minus allowance from table XIII.is illustrated in figure XTII.1408 .3790 . D Piicn diameter. col 8.9400 1.2112 .4700 .0302 . D.03125 .0845 .5500 .2312 .04167 .8900 2.6.4224p diameter.3900 1.25000 .0704 .2112 10 (teg min 4 94 4 28 4 20 3 41 3 92 3 4 3 3 3 3 3 3 2 2 2 2 2 3 2 2 2 1 52 20 41 52 25 4 30 12 43 22 50 32 18 12 43 22 6 53 1 M Mt i" in.03750 . col 3.10000 .3. H 16 14 12 12 10 8 6 6 5 5 5 4 4 4 4 1 3 3 2 2 2 2 2 0.05000 . K=-D-2k 5 Pitch. p.33333 .90000 .03000 .08333 .2000 3.19000 .3. col 7.90000 ft.04167 .6900 .5879 . 0.25000 .10000 .07500 . Max pitch diam=Int min pitch diam minus allowance from table XIII.05000 .25000 .8290 .il29 .1290 1.03572 .4000 2. 6.1408 .25000 . hasic diameters and thread data Basic diameters Thread data Nominal sites Threads per inch.10000 . and on tools and gages: Right-hand thread: Vr. col 8.2500 . col 5.3.08333 .OUOO 1.4375 .06000 .25000 .19000 .07500 .2.2125 .3290 .7500 3.3879 .4290 1.12500 . 0.9000 9.1056 . col 3.4400 .9000 2. col 4. (Basic) Min pitch diam=Ext max major diam minus basic height of thread from table XIII.6. 0.2.p Thread thick.3500 3.6500 2.9500 2.10000 .7900 2.2606 .: m 1M m 1)4 1H 2 2M 2H 2H 3 t\i 4 4H 6 21 .10000 .33333 .0845 .Basic height ness at pitch of thread.0264 .0690 1.***S .6000 1.15000 .07500 .01875 . Min major diam=Ext max major diam minus tolerance from table XIII.1500 2.15000 Basic width Lead angle of flat.12500 .10000 .1900 1.-20 STUB ACME '—Right hand (since designation LH is not specified) -Thread series -Number of threads per inch 1 —Nominal size in inches Left-hand thread: VT -20 STUB ACME—LH Left hand Thread series Number of threads per inch 1 —Nominal size in inches "C TABLE XIII.8750 l.10000 .1096 . Max minor diam=Int min minor diam plus tolerance from table XIII.33333 .6750 1.0422 .16667 .2000 4.0000 6 in.2112 .2112 .0000 3.06000 .629. f-p/2 7 in.9250 2.7000 3.2. Min minor diam=Ext max major diam minus 2 times basic height of thread from table XIII.16667 .8900 4.8900 Minor diameter.0000 4.0845 .25000 . at basic pitch F=0. 0.08333 . (Basic) Max pitch diam=Int min pitch diam plus tolerance from table XII.0000 2 2500 2. »=0. Min pitch diam=Ext max pitch diam minus tolerance from table XII. col 6.5000 1.02143 .12500 .7000 u i H H :.06000 . Min minor diam=Ext max minor diam minus tolerance from table XIII.' .8900 3.3p line.3000 2. E-D-k 4 in.2.1408 . p.1300 1. X 9 in. The values in table XIII.12900 .2290 1.3125 .—Standard Stub Acme thread series.n Major diameter.02500 . Internal Threads (Nuts) Min major diam=Ext max major diam plus allowance from table XIII. col 7.2911 .20000 .0050 1.7000 4.3.0528 .0352 .25000 .29000 8 in.2500 1. 0.3900 4.15000 .4.2112 .0352 . 0.06250 .02500 .7750 .07143 .16667 .3.5000 4.1056 .7500 .8800 1. 2 3 in. Max major diam=Int min major diam plus tolerance from table XIII.0704 .12900 .08333 .20000 . .20000 .07500 .10667 . 3.020 . 0. p.020 . These threads are identified as Modified Form 1 Stub Acme Thread (shown on fig.020 .4). 0. b An increase of 10 percent in the allowance is recommended for each Inch.020 . It Is recommended that the nominal sizes given in table XIII.0137 .020 . 0100 . and for modified form 2 the pitch and minor diameters will be larger than those dimensions for the standard forms.05p threads threads plus minus Tolerance on * major diameter.0050 .020 6 in.010 .0050 .0250 6 in. 7 for standard Stub Acme threads. tol.3. also tolerance on minor diameter.022» .0154 .010 .0263 .020 . the allowances and tolerances can be taken directly from tables XIII.020 .n diam.0100 .6.020 .0062 . ALTERNATIVE STUB ACME THREADS Recognizing the fact that the standard Stub Acme thread form may not provide a generally acceptable thread system to meet the requirements of all applications.010 .020 .0083 .020 .020 .010 . 0167 . • The minimum clearance at the major diameter between the internal and external threads is equal to column 3. 22 .020 .0125 . the pitch factor is used as a base.0104 .0050 .020 .020 .020 . such as on thin-walled components. These threads shall be designated as shown below on drawings and in specifications.0125 . XIII. 0050 .D.0250 .0050 .0050 . minus on all external threads. and on tools and gages: Right-hand thread: -Modified Form 1 )4—20 STUB ACME Ml H—20 STUB ACME M2 Modified Form 2 Left-hand thread: Yr-20 STUB ACME Ml-LH M-20 STUB ACME M2—LH TABLE XIII.0123 . -1.—Plt~h diameter allowances for Stub Acme threads Nominal size range • Fitch diameter1' allowances on external threads. 0250 . basic data for two of the other commonly used forms are tabulated in tables XIII. however. These values are calculated from the mean of the range.0167 .50 . the standard Stub Acme Thread form should be used. plus all in.11125 .0125 .0125 .020 .0332 . 0.7. diam.0324 .—Tolerances and allowances for major and minor diameters.4.020 .005 in.0125 .3) and Modified Form 2 Stub Acme Thread (shown on fig.020 .6 and XIII.017» .0126 .020 .0062 .0105 . 0167 . diameter.0346 M H» « hi H H - 16 14 12 12 10 8 6 6 5 5 «. 0.020 . ■ Tlie values in column 3 are to be used for any nominal size within the range shown in cols 1 and 2.0167 . » I or an intermediate size. 11250 .020 .QXP.0050 .0250 . 0167 . • To avoid a complicated formula anil still provide an adequate tolerance.0201 . J The minimum clearance at the minor diameter between the Internal and external threads is equal to column 4.010 .020 . 0125 .7.2 and XIII.0268 .020 . 0.020 . the tolerances and deviations for the next larper size given in this table shall apply.020 . 0. 0167 . with the minimum tolerance value set at 0.4.0050 .5.0083 .- u 1 1)4 1M Hi 1)4 IM 2 2« «M 2H 3 3H 4 4)5 - — 5 4 4 4 4 3 3 3 2 2 2 2 2 « » Pitch-diameter tolerances for various practicable combinations of diameter and pitch are Riven In table XII.11083 . Stub Acme threads * Allowances from basic major and minor diameters Tolerance • Tolerance • on minor on major Threads diameter.0050 . In applying the foregoing data to special designs.020 . 7.6. XIII.00.0125 . 0100 .020 .020 4 in.008-/D 1 in.2 be used whenever possible.0100 .020 .020 .0250 .020 .02.010 . threads.020 .01!« . p. Therefore the major diameter and basic thread thickness at pitch line for both external and internal threads will be the same as for the standard form as shown in tables XIII.033» . per Major« MinorJ all internal all external inch. Size» TABLE XIII.0083 . Wherever practicable.all exminus ternal ternal 0. XIII.010 .010 .020 .020 .50 . or fraction thereof.031« .0223 . 2 3 in. that the length of engagement exceeds two diameters.0250 7 in. 0250 .05p 0.OHM .2 and XIII.0100 . and XII.0220 . 0250 . the pitch and minor diameters will be smaller than similar values for the standard form. threads.0235 .020 .0174 . ' For use only where the major diameter of the internal thread and the minor diameter of the external thread must be controlled. The pitch diameter and minor diameter will vary from the data shown in tables XIII. for modified form 1.020 .5.0114 . 0273 . plus on all Internal threads. 020 . saa •8 s .85 «•si h>9r- III IP 1§§ 000 sgg ooS© ecoc «no fcSS ?$3 g I2 »no»-* 1* S0 SSo ©c*c» 5«.«".£.5f.885? ■HlSS 111 »I'M 4SI 111 — 383 S3 3 t-i-c SP 512 fcar? ill oiffi gjej — as*© III S fei -3te2 •-SSo •oeac ■2Rf3 = fsi II 8RS |S3 ?S3? lit IKS 3? to SSI 133 | S .^ Wm© 38S »-TO *SS = in to-rite iss 5^S 8ss rt«S 1 •a BBS X nriO |fSS3 888 W .ass 11= III Iii 2t§ ass S3c5S «N8 •SSS peg ass •säsä Ssrs «äs S5^ =r e 55s- 5£H s5o s5» a «•.8 &3 *rt a ■3 III iii §11 JS| 2$ sag ?3S 80S 888 sss .«».=sss sss 4ii .888 883 .ZSf- E ■5 e a E 5 s 2 u 5 a 23 . NOTATION p-pitch «-basic thread height 24 .2.INTERNAL THREAD (NUT) EXTERNAL THREAD (SCREW) FIGURE XIII. and crest clearances for Stub Acme threads.—Illustration of allotvances. tolerances. and that a minimum-metal limit or "not go" thread gage can effectively check but one element. 3. column 4.0725 .02500 .06250 . 2. 3.0504 . or 0.0622 .04167 .0363 .08333 .1343 .0576 . The dimensions of "go" and "not go" gages should be in accordance with the principles: FIGURE XIII. 0.20000 .0672 .— The major and minor diameter tolerances for Stub Acme thread gages are given in table XIII.16667 .0933 .4353 16 14 12 10 9 8— 6 8 4 7 EXTERNAL THREAD (SCREW) m 3 2M 2 FIGCRE XIII. TOLERANCES ON PITCH DIAMETER. TABLE XIII.12500 .50000 .'■::■'Z'.03571 .37500 .4030 16 14 12 10 9 8 7 6 5 4 8H 3 2H 2 Hi m i • Allowance Is shown In table XIII.4353p Tolerances for the thread elements of "go" and "not go" thread gages for Stub Acme threads are as specified below. for gages with a length over 5 to 10 in.2600 .1451 .25000 . inclusive. and (6) that permissible variations in the gages be kept within the extreme product limits. f-p/2 n l P allowance" ft.03750 . Threads per Inch.0003 in.01786 . -0.10000 . 1975 . Thread thickness (basic).0004 in.250p Total height of thread.4. 1.06250 .—The pitch diameter tolerances for gages for external and internal threads are given in table XIII.25000 .03125 . h-0.0378 .06250 07143 .0007 in. F„ -0.0544 . TOLERANCES ON MAJOR AND MINOR DIAMETERS.0517 .0484 .4030p Threads per Inch.2600 INT ERNAL THREAD (NUT) ÄÄÄ.16667 .}T5p --»- 2 in.1741 .0363 .0413 .33333 . are necessary for the proper inspection of Stub Acme threads.0403 .0728 .6.50000 . Pitch.37500 . col.1171 .1600 . between any 2 threads not farther apart than 1 in.75000 1.3265 .0600 .2687 . 07500 . 05556 .. 0. 0.18750 .0336 . Thread thickness (basic).14286 .04167 .07143 .08333 . GAGES FOR STUB ACME THREADS Gages representing both product limits.40000 . 0.1767 .10000 . * Allowance Is shown in table XIII.14286 .06250 . column 4.09375 .05000 .0311 .28125 .50000 6 in.401100 . However. 0.—Modified Form 2 Stub Acme thread with basic height of 0.0258 .00000 3 in.20000 .03125 . inclusive. ft-0." gage should check simultaneously as many elements as possible. 12500 .04167 .05357 .07143 .25000 5 in.10000 .10000 . 07143 08333 .25000 .18750 . or "go.0517 .0206 .75000 1.8.. 0475 . 2. 0.20600 .1244 .0850 .1088 . 25 .2177 . basic dimensions Width of flat at crest of Internal thread (basic).04167 .03125 .0435 .0636 .01563 .. 0.28571 .12500 . 0267J .TABLE XIII.33333 ..■//'■■ ■'. col.0448 .12500 . 0.0871 .02778 .10118 .25000 . f-p/2 (a) that the maximum-metal limit.2015 .1038 . or adequate gaging instruments for thread elements.33333 . the cumulative deviation in leatl shall not exceed 0.1975 .50000 6 in.-»+tt 4 in.7.1100 .2902 . Height of thread (basic). »-0.07143 .375p Total height of thread.12500 . m m i ////.14286 .0350 .375 pitch.0252 .1151 .-TIIC variation in lead of all Stub Acme thread gages shall not exceed 0.3850 1 2 in. 0725 . 1350 .03571 .02083 .15000 .0806 . For multiple threads the cumulative tolerance for any length of gage shall be obtained by multiplying by 1.0288 . INTERNAL THREAD (NUT) 8.25 pitch.16667 .0284 .0814 .8.—Modified Form S Stub Acme thread form. for gages with a length over 3 to 5 in.10000 .3.0272 .11111 . 0. or 0.25000 . basic dimensions Width of flat at crest of Internal thread (basic).3.16867 .60000 3 in.14286 . 0.03125 . TOLERANCES ON LEAO.0005 in. for gages with a length over 1 to 3 in..3023 . 03572 .66667 .3.0229 .37500 5 in. n Pitch.11111 .08333 .02344 .. F.0569 . Height of thread (basic).66667 .2913 .04688 .05000 ..5 the above tolerance applicable to that length. 16667 .08333 .33333 .06250 .12500 . (a) GAGE TOLERANCES P allowance* ft. 0318 . inclusive.1612 . 10714 .05556 .20000 .0457 .1350 .—Modified Form 1 Stub Acme thread form.28571 .-ft+H 4 in.—Modified Farm 1 Stub Acme thread with basic height of 0.05000 .06250 . p. are tolerances on one-half the included angle.002 .0018 .00020 .002 .—The minor diameter shall be cleared below the minimum minor diameter of the "go" thread ring or snap gage.0021 10 10 10 10 10 8 8 8 8 8 8 0 6 M fi 5 5 5 • Intermediate pitches take the tolerances of the next coarser pitch listed in bthis table.002 . "GO" GAGE. 6.00025 4 in. or slight projections on the thread form. and shall be applied minus. should not exceed the tolerances permitted on angle of thread. Tolerances are shown in table XIII. o.15p. or the gaging dimension of the "go" plain snap gage.—The major diameter of the "not go" thread ring or thread snap gage shall clear a diameter greater by 0.000 3 in. 0.825 1. (d) Length.—The length shall approximate three fetches except that.8.00012 .—The length shall be at least equal to the length of the "not go" thread ring or snap gage.—The minor diameter shall be the same as the maximum minor diameter of the external thread plus 0. 4. 2. except when modified in accord26 (d) length. (b) OAQES FOR EXTERNAL THREADS XIII. "NOT GO" THREAD RING OR THREAD SNAP GAGE. 0.002 . 3.510 4. with the tolerance applied plus. .010 in. 4.00050 1*. 4 for the various pitches. the maximum-metal limit thread setting plug gage.0013 .—The major diameter of the "go" thread ring or snap gage shall clear a diameter greater by 0.—The minor diameter shall be cleared below the minimum minor diameter of the "not go" thread gage. that Is.002 . shall be the same as the maximum major diameter of the external thread. (c) Minor diameter.001 . (b) Pitch diameter. 4.0014 . p. than the maximum major diameter of the external thread. (6) Pitch diameter. Stub Acme threads Tolerances on Tolerance on pitch diameter b major and minor diameters 2 in.0009 . the ength shall provide at least one full turn of thread.— (a) Major diameter. than the maximum major diameter of the external thread.002 Threads per inch » 1 16 14 12 10 9.—The pitch diameter shall be the same as the minimum pitch diameter of the external thread. TOLERANCES ON ANGLE OF THREADS.825 1.0010 .0009 . Tolerances are shown in table XIII. The equivalent deviation from the true thread form caused by such irregularities as convex or concave sides of the thread. as specified in table XIII. The gage tolerance shall be applied plus.14. for pitches finer than 10 tpi and plus 0.510 5.—(a) THREAD RING OR THREAD SNAP Major diameter.—The major diameter of the maximum-metal limit thread setting plug shall he the same as the maximum major diameter of the external thread.—The pitch diameter shall fit. This insures that the bisector of the included angle will be perpendicular to the axis of the thread within proper limits. The gage tolerance shall be applied plus.— (a) Major diameter.0006 . 3.010 in.0008 .510 2. (c) Minor diameter. (d) Length.510 4. col.0011 .—(a) Major diameter. MAXIMUM-METAL LIMIT THREAD SETTING PLUG FOR "GO" THREAD RING OR SNAP GAGES. (6) Pitch diameter.too . These pitch diameter tolerances for thread gages are not cumulative. ance with table XII.00040 . (d) Length. they do not include tolerances on lead and on half angle.510 2. col. Stub Acme threads Site range Tolerances for plain plug gages Tolerances for plain ring and snap gages Above 1 To and Including 2 in.002 .TABLE XIII.9.0015 .00016 .002 .002 . 5. and shall be applied plus. 3 in.00010 .—The pitch diameter shall be the same as the maximum pitch diameter of the external thread.—The length shall approximate the length of the "go" thread ring or snap gage. for multiple threads. 17. for 10 tpi and coarser.002 . (6) Pitch diameter. with the tolerance applied plus.00032 .—The major diameter of the minimum-metal limit thread setting plug shall be the same as the maximum major diameter of the external thread.002 .0007 .0008 . 8 7 6 5 4 3'A 3 2H 2 0. col. col.00024 .9.9.01 in.001 .510 1.005 in.0013 .0006 .—Tolerances for plain gages. MINIMUM-METAL THREAD SETTING PLUG FOR "NOT GO" THREAD RING OR SNAP GAGE. (c) Minor diameter. Tolerance on half angle of thread 4 minute» 0.0018 . 0.00020 .002 .—The tolerances on angle of thread.—The pitch diameter shall fit the minimum-metal limit thread setting plug gage.8. "GO" PLAIN RING OR SNAP GAGE FOR MAJOR DIAMETER.—The diameter of the "go" plain ring gage.002 . "NOT GO" PLAIN SNAP GAGE FOR MAJOR DIAMETER.—The gaging dimension of the "not go" plain snap gage shall be the same as the minimum major diameter of the external thread. 14. The tolerance shall be applied minus.0006 . 17.002 .—The minor diameter shall be the basic minor diameter of the internal thread plus 0.001 .—Tht length shall approximate the length of engagement but shall not exceed the length specified in table XII. TABLE 4.—Tolerances for "go" and "not go" thread gages. (c) Minor diameter. (c) QAGES FOR INTERNAL THREADS 1. "GO" THREAD PLUG GAGE.-(a) Major diameter.-The major diameter of the "go" thread plug gage shall be equal to the minimum major diameter of the internal thread minus 0.005 in. for pitches finer than 10 tpi, and minus 0.010 in. for 10 tpi and coarser. The tolerance (table XIII.8, col. 3) shall be applied plus. (6) Pitch diameter.—The pitch diameter shall be equal to the minimum (basic) pitch diameter of the internal thread, with the tolerance (table XIII.8, col. 2) applied plus. (c) Minor diameter. —The minor diameter shall clear a diameter smaller by 0.010 in. than the minimum minor diameter of the internal thread. (d) Length.— The length shall approximate the length of engagement (see footnote to table XII.14, p. 17) but shall not exceed twice the nominal major diameter, unless otherwise specified. 2. "NOT GO" THREAD PLUG GAGE FOR PITCH DIAMETER OF INTERNAL THREAD.—(O) Major diameter.—The major diameter of the "not go" thread plug gage shall be equal to the maximum (basic) major diameter of the external thread minus 0.l5p with the tolerance (table XIII.8, col. 3) applied minus. (6) Pitch diameter.—The pitch diameter shall be the same as the maximum pitch diameter of the internal thread, with the tolerance (table XIII.8, col. 2) applied minus. (c) Minor diameter.—The minor diameter shall clear a diameter less by 0.01 in. than the minimum minor diameter of the internal thread. (d) Length. —The length shall approximate three pitches, except that for multiple threads the length shall provide at least one full turn of thread. 3. "GO" PLAIN PLUG GAGE FOR MINOR DIAMETER OF INTERNAL THREAD.—The diameter of the "go" plain plug gage shall be the same as the minimum minor diameter of the internal thread. The gage tolerance shall be applied plus. (See table XIII.9, col. 3.) The gage length shall be in accordance with the latest revision of Commercial Standard CS8, Gage Blanks. 4. "NOT GO" PLAIN PLUG GAGE FOR MINOR DIAMETER OF INTERNAL THREAD.—The diameter of the "not go" plain plug gage shall be the same as the maximum minor diameter of the internal thread. The gage tolerance shall be applied minus. (See table XIII.9, col. 3.) The gage length shall be in accordance with the latest revision of CS8, Gage Blanks. (d) CONCENTRICITY When a special check of the concentricity between the major, pitch, and minor diameters of an external or internal thread is required, the method of checking this concentricity must be devised for each individual application. (e) GAGE DIMENSIONS SECTION XIV. NATIONAL BUTTRESS THREADS6 1. HISTORICAL Although the Buttress thread was described as early as March, 1888 in the Journal of The Franklin Institute, it was so little used that its national standardization was not undertaken until after the Combined Conservation Committee in early 1942 reviewed the standardization status of items needed in the war effort. Formerly each application of the Buttress thread was treated individually and the form it took depended on the experience of the designer and the manufacturing equipment available. At the American-British-Canadian conference in New York, called by the Combined Conservation Committee in November, 1943, Buttress threads were discussed and it was agreed that a basic profile should be established for this thread, that the Interdepartmental Screw Thread Committee (ISTC) of the War, Navy, and Commerce Departments should collect data on current practice of American producers, and that the American Standards Association should distribute the data for comment from industries using Buttress threads. As the Military Departments needed Buttress and other special types of threads, the War Production Board in February, 1944, arranged with the ASA to establish a General War Committee on Screw Threads. In April 1944, F. E. Richardson, then with the Aeronautical Board and a member of the ASA War Committee on Screw Threads, collected information on Buttress threads and presented it at a joint meeting of the Bl Sectional Committee on the Standardization and Unification of Screw Threads, the Interdepartmental Screw Thread Committee, and the General ASA War Committee on Screw Threads. The data disclosed that the pressure flank angle, measured in an axial plane, ranged from 0 to more than 15° from the normal to the axis, and the clearance flank angle ranged from 30 to 55°. The ISTC decided to develop a Sroposed Buttress thread form having a pressure ank angle of 7°, which closely approaches the static angle of friction for well-lubricated steel surfaces in contact, and a clearance flank angle of 45°. At the American-British-Canadian conference in London, August and September, 1944, sponsored by the Combined Production and Resources Board, the British proposed a Buttress thread of 7.5° pressure flank angle and a 45° clearance flank angle. The United States' proposal was the ISTC's recommendation of a 7° by 45° thread [>rofile. The British agreed to prepare and circuate a draft specification for a Buttress thread having a 7° pressure flank angle, a 45° clearance • This section is in substantial agreement with American Standards Association publication ASA B1.9, Buttress Screw Threads, which is published by the ASME. 2» W. 3Wh Street, New York 18, N.Y. The latest revision should be consulted when referring to this ASA document. It is recommended that wherever possible the general dimensions of the gages be in accordance with the latest revision of CS8, Gage Blanks. 550170*—60 3 27 flank angle, and a basic depth of thread engagement cf OAp. It was also agreed that the specification should include recommended relationship of 'pitch to diameter and appropriate tables of clearances and tolerances for such relationships. The 1944 edition of Handbook H28 published the ISTC's recommendation of a basic Buttress thread form which had a crest flat in the internal thread (nut) twice that of the external thread (screw), and a thread engagement depth of approximately 0.56p. In November, 1944, the ASA War Subcommittee on Buttress Threads was established and after reviewing the British draft of April, 1945, this committee felt that because of the distortion tendency of thin wall tubing, a greater basic depth of thread engagement than OAp was desirable, especially since the minimum depth of thread engagement is necessarily less than OAp by one-half the sum of the allowance and the tolerances on minor diameter of internal thread and major diameter of external thread. Therefore, the July, 1945 draft of the War Standard was based on a basic depth of thread engagement of 0.5p. Another American-British-Canadian conference sponsored by the Combined Production and Resources Board was held in Ottawa, Canada, September and October, 1945. Here the British proposal of April, 1945, with an alternate design of 0° pressure flank angle and a clearance flank angle of 52°, was reviewed and compared with the American proposal of July, 1945. Learning that the British had had considerable favorable experience on thin wall tubing with Buttress threads having OAp basic depth of thread engagement, it was decided that the American standard might adopt this basis. Accord was also reached v.-< preferred diameters and pitches, thread dimension tolerances and allowances, and on having each standard include in its appendix an alternate thread of 0° pressure flank angle. Further, each country agreed to publish the standard in conformance with their respective formats. In April, 1946, buttress threads were assigned to Subcommittee No. 3 of the Sectional Committee on the Standardization and Unification of Screw Threads, Bl, and the committee membership was enlarged. This committee prepared and circulated in 1948 to members of the Bl committee, a draft of a proposed standard based on the British proposal with a basic thread depth of OAp. The comments included so many objections to the shallow depth of thread that in 1949 the committee decided to base the next draft on a thread having 0.6p engagement depth. The committee also voted not to include in the appendix of the American standard, data for a buttress thread having 0° pressure flank angle as it was evident that this was only one of several modifications that might be needed for special applications. The next American-British-Canadian conference was called at the request of the Director of Defense Mobilization and held in New York in June, 1952. The British Standard 1657; 1950 for Buttress 28 Threads which is based on a thread engagement depth of OAp and the American draft of September, 1951, based on thread engagement depth of 0.6p were reviewed. It was concluded that the applications for buttress threads are so varied that threads with either engagement depth (OAp or 0.0p) might be preferred for particular design requirements. It was recommended that the next printing of the British standard and the forthcoming American standard include the essential details of the other country's standards in appendixes. ASA Bl.9-1953, Buttress Screw Threads, was issued in conformance with this recommendation. 2. GENERAL The Buttress form of thread has certain advantages ;n applications involving exceptionally high stresses in one direction only, along the thread axis. As the thrust side of the thread is made very nearly perpendicular to the thread axis, the radial component of the thrust is reduced to a minimum. On account of the small radial thrust, this form of thread is particularly applicable where tubular members are screwed together. Examples of actual applications are the breech mechanisms of large guns and airplane propeller hubs. As the use of buttress threads applies mainly to specially designed components, it has been considered that no useful purpose would be served by introducing a recommended diameter-pitch series. In selecting the form of thread recommended as standard, manufacture by the thread milling or grinding processes has been taken into consideration. Wherever possible it is recommended that the form of thread and tolerances contained in this section be used. 3. SPECIFICATIONS 1. SCOPE.—This section relates to threads of buttress form and provides: (a) a standard form of thread, (6) tables of preferred diameters and preferred pitches, (c) a formula for calculating pitch diameter tolerances, (d) tolerances for major and minor diameters, (e) a system of allowances between mating parts, and (/) recommended methods of gaging. 2. DEFINITIONS.—The pressure flank is that which takes the thrust or load in an assembly. The clearance flank is that which does not take the thrust or load in an assembly. 3. BASIC FORM OF THKEAD.—The basic form of the buttress thread is shown in figure XIV.l, and has the following characteristics: (a) a pressure flank angle, measured in an axial plane, of 7° from the normal to the axis; (6) a clearance flank angle, measured in an axial plane, of 45°; (c) equal truncations at the crests of the internal and external threads such that the basic depth of engagement (assuming no allowance) is equal to 0.6p; {d) equal radii at the roots of the internal and external threads tangential to the pressure flank and the clearance flank. 4. PREFERRED DIAMETER SERIES.—It is recommended that the nominal major diameters of buttress threads be selected wherever possible from the following geometric (20) series: INCHES It is to be borne in mind that this formula relates specifically to class 2 (medium) tolerances. Class 3 (close) tolerances are % of class 2 (medium) tolerances, and class 1 (free) tolerances are 1){ times class 2 (medium) tolerances. If the length of engagement is taken as 10p, the formula can be further simplified to: PD tolerancc=0.002V5+0.0173Vp. Using this formula, pitch diameter tolerances for various combinations of pitch and diameter are given in tables XIV.2, XIV.3, and XIV.4. (6) Tolerances on major diameter of external thread and minor diameter of internal thread.—As each of these diameters may be used as a datum INTERNAL (NUT) 1 % % % % X« % lYi l% n VA 2A 2% 3 VA i« 2 2% 4 4% 5 5% 6 7 8 9 10 11 12 14 16 18 20 22 24 5. PREFERRED PITCH SERIES.—It is recommended that the pitches of buttress threads be selected from the following geometric (10) series: Threads per inch 20 16 12 10 8 6 5 4 3 2A 2 0.020p RADIUS, APPPOX (OPTIONAL) VA i ix The following suggestions are made regarding suitable associations of diameters and pitches: Diameter range in. From Hto'Me Over>M«tol Over 1 to 1H Over Hi to2H Over 2H to 4 Over 4 to 6 Over 10 to 16 Over 16 to 24 Associated pitches (pi 20.16,12 16,12,10 16,12,10,8,6 16,12,10,8,6,5,4 16,12,10,8,6,5,4 12,10,8,6,5,4,3 10,8,6, 5,4,3,2V*. 2 10, 8, 6, 5, 4, 3, 2M, 2, 1H, IM 8, 6, 5, 4, 3, 2V<>, 2, IV<, IM, 1 EXTERNAL FIOURE THREAD (SCREW) XIV. 1.—Form of Buttress thread having 7° pressure flank and 45° clearance flank. NOTATION Max material (basic) Nominal major diameter Height of sharp-V thread Basic height of thread Root radius Root truncation Allowance Depth of engagement D r/«0.89064p A-0.6p r-0.07141p »-0.08261p A.-n-0/2 Min material (see footnote) Min r«0.0357p Min »=Max «/2-0.0413p Mln A.-Maxft.-lMtol. on major diam external thread (screw)+ M tol. on minor diam Internal thread (nut).| Max 0»-Max pitch diam of Internal thread (nut) +0.80SÖP. Min A',-Min pitch dlam of external thread (screw) -0.80803p. Basic dimensions for each of the foregoing pitches are given in table XIV. 1. 6. TOLERANCES.—Tolerances on external threads shall be minus, and on internal threads shall be plus. (a) Tolerances on pitch diameter.—The following formula is used for determining pitch diameter tolerances: Class 2 (medium) pitch diameter: PD tolerance=0.002VZ)+0.00278v^+0.00854Vp where D=major diameter of thread, L.=length of engagement, p—pitch of thread. a Crest truncation /-0.14532p F-0. 16316D Crest width Major diameter of internal V.* D+0.12542p thread (nut) Minor diameter of external K>ß-1.32542p thread (screw) -O Height of thread of Internal thread (nut) Height of thread of extcrmil thread (screw) »„-0.06271p /i,=0.6G271p NOTE: The formulas for "Min material" given above apply when an adequate wall thickness Is provided beyond the roots of the threads. For Buttress threads on relatively thln-wallcd tubing the root truncation <-0.08261p may bo taken as the minimum truncation and the maximum truncation recommended Is O.0826Ip+G/2. This will give max «»-max pitch diam of internal thread (nut)+0.72542p and mln Tf.-ndn pitch diam of external thread (screw)— 0.72542p. In order to avoid contact between the crest corners of "go" thread gages and the maximum root radius, the crest corners on the pressure flank of "go" thread gages should be bevelled a radial distance approximately equal to 0/2. 29 0103 . 3.00774 .0102 .002 Preferred diameters 20 16 12 10 8 6 1 6 1 4 3 2M 2 m in.009'. in.8. in.0061 .0082 .H.0077 .0169 0.0074 «.0041 .0291 .0037 0.0060 . 1H.0074 .0127 .0096 0. IM 1 Tolerance on pitch diameter.0063 .0060 .—Basic dimensions for Buttress threads ' Basic height of thread.0093 0.10 11.0124 .0080 0090 0100 Major diameter Diameter increment.0300 .0103 . class 2 (medium) Threads par inch Tol on major dla ofext thread and minor diaofint thread in. .6000 4 in.16 18. class 3 (close) Threads per inch Tol on major dia ofext thread and minor dlaofint thread in.01413 .2969 .0080 .0064 . 0. . F=0.24 in. in.H. in.0.1657 .1163 .0112 .0060 .0363 . orA.0112 1?*.0600 .1088 . in.1632 20 16 12 10 8 6 ( 4 3 2H 2 m Jg:::::::::::::: i :.2209 .6p Height of sharp V thread.3.0089 .0071 .0060 .. in. .0118 .4 .0130 ..0476 .0414 .0080 0.20. in.7126 . tf=0.0083 .0445 .4 4W.22.0042 .1463 7 in.0551 .4000 3 in.8000 1.01094 .0088 in.--.0040 .0066 . .0091 .0115 .00706 . in.1667 .0500 .1484 .0196 . ft=0. 2M to 4 .0357 .0286 .0165 .12.—Tolerances on Bui'ress threads.0113 0.0067 .0121 0 0134 .0046 0.0714 9 in.0070 . .0066 0. 6.0045 .0098 . . 0. 2H 2?4.1260 .07141p Width of flat at crest.24 .0089 .00215 1 tolH lHto2M.0572 . 1.0118 . in.0408 . in. r=0.0141 .ÖJ88 0.0121 .0727 . in. in.1M.0138 .0058 .0059 .0163 .0046 .08261p Root radius.2. 0143 .M. Hto'M« -.0139 O.0117 .7. TABLE XIV.00400 .3333 .00999 .0742 .00296 2Htto4 4 to6 6tol0 10 to 16 16 to 24 .00647 .0072 .4000 .0.00612 .0275 «130 .8.0413 . in. 10--11.4418 .0179 .2000 .0074 . in.0068 . in.0135 .14532p Height of thread.0271 .2.2600 .0053 .0050 .0154 .0331 .16 18. 4to6 6 to 10 10 to 16 16 to 24 . 1326 .9. in.0040 0. n.0111 . 0.0816 . IM 1M.0145 . 0..0164 .1 .0134 .0149 0.0078 . Hto'M« -->M«tol ltolM .0053 .0108 .2661 .00643 in.2400 .0177 .8906 5 in.0056 0.'M.22.1113 .00387 .0036 .0238 .3563 .0077 .14.1106 .0661 .0080 ..01547 .0075 .6302 .0080 Major diameter Preferred diameters 20 16 12 10 8 6 5 4 3 24 2 1W IM ' in. in.0067 .6000 . in.0074 .4800 . Tolerance on pitch diameter. 0.0116 4M.0101 .0126 .0600 .0089 .0552 .3314 .00470 .0060 0.0060 .3)4.0969 .20.0040 .0069 0. Ji.0071 . 2M.0062 .0140 0.0095 ...6 7.2M.0227 Pitch increment 0.0048 .0204 .9.0376 .0242 .1M.H«.1W .0073 .0132 in.0663 .0828 .0083 0. 3.0826 8 in.0061 .6667 .0102 .0050 0070 .1000 .0052 .6.0000 • Symbols are shown on figure XIV.0084 .008» .01223 .1781 . »-0.0068 0.0760 . H.1305 .2227 . in.0066 .0107 .0109 .00409 .00866 .0484 .16316p Threads per Inch Pitch.00262 .3000 . 0. i 1M.0071 . P 1 2 in.6938 .0326 .12.:::.'ÖIK TABLE XIV.0100 .= 0.0182 .0136 .0059 .0040 .0030 .0049 .0104 .00168 'Hi tol.0833 .0051 0. in.2.0066 .0126 6. 0. n.0106 .0084 .2W---2M.2000 . in.0078 . 5.0557 .0083 ..00189 . 1H.6627 Root truncation.0094 . in.0060 . 0. in. 0.0108 .00342 .0083 .lMto2H .0891 .4463 .0084 . 0.0625 .0166 .0044 . external and internal threads in.0162 .0100 0.0030 .0147 .14.0086 .0681 . /=0.1200 . 5H.TABLE XIV.01O3 0.0543 .0064 0.66271p 6 in. 3W. 0.017 3 V^" .0091 .0076 0.0069 .0119 .l.0207 . 0.0070 .89064p Crest truncation.1000 . in. external and internal threads in.0092 1H.5M.01730 30 .00432 .0073 .0067 .'H» H.0068 .0043 .0209 0..0049 . in..W«.0202 .—Tolerances on Buttress threads.0663 .1600 . 2M.20.0080 . in. The amount of the allowance should be deducted from the nominal major.0181 0.0050 .0088 if«.0040 00044 .14. in.5.0061 .0210 0.0060 .0104 .0107 . —--pitch diameter allowance on external thread t»root truncation XIV. all classes Threads per inch Major diameter Preferred diameters 20 16 12 10 8 6 5 4 3 m in. The disposition of allowances and tolerances is indicated in figure XIV. TABLE INTERNAL THREAD (NUT) EXTERNAL FIGURE THREAD (SCREW) XIV.—It will be sufficient in most instances to state only the maximum minor diameter of the external thread and the minimum major diameter of the internal thread without any tolerance.0048 .0064 .0080 0. In. H.0072 .0118 . 6(a). 4 tot 6 to 10 10 to 18 16 to 24.0074 . IX ' Tolerance on pitch diameter.0120 .1M 2. in. and major diameter oj internal thread.iH m in. class 1 (free Threads per inch Tol on major di.0098 .0113 .TABLE XIV.4 4M.2H 2*4.0058 .0211 .Ö3Ö3 .0157 .0083 0.01155 a 0081 . in. in. minor.0103 .4.0265 .i of cxt thread and minor Major diameter Preferred diameters 20 16 12 10 8 6 S 4 3 IVi 2 m in.0093 .22.3. 0 0050 .0187 .—An allowance (clearance) should be provided on all buttress external threads in order to secure easy assembly of parts. in.0124 0. and pitch ditmeters in.0050 .008» .0049 . The recommended allowance is the same for all three classes of thread and is equal to the class 3 (close) pitch diameter tolerance as calculated under par. in. in.0197 .16 18.4.0119 in.0167 .12.1M. in. .2. 7.6 7.0042 .24 - to.0051 0.0100 0.3.0094 .0190 .22.0236 .0314 0.1H l?i.0113 0.0108 .0071 .0087 .5*4.8.0078 .0139 0.0142 for measurement of thread angles and pitch they should be held to close limits.—Allowances on external Buttress threads.24 iu. 0.0043 . in. in. in. the root truncation from a sharp V should not be greater than 0.0168 . ^.öiii .0090 0. in.0126 0.ni.0144 0. y.0083 .?i6.0160 .10 11.0110 0130 .0056 .0413p.0053 .12.2.1 .0130 .5. in.0282 Ö.9.0046 . in.0133 .14.1 1H.4 --7. in.0341" in. in.0173 .3^.0070 . XIV. 5.0084 .0064 0. 6 to 10 10 to 16 16 to 24 H to'M» in. in.0077 . in.0143 . pitch.0059 . Buttress threads.0176 .0174 .0109 . H.0130 .0063 .0826p or less than 0.0100 .0246 . (c) Tolerances on minor diameter of external thread.0200 .0136 .0068 0.0176 .0104 . and root truncations.0164 0. in. The minimum internal thread diameters will be basic. 0.0074 .^.M.0037 0. to >H« l tolVs M to 4.W».0166 .0152 31 . and XIV.16 18. and minor diameters of the external member in order to determine the maximum metal condition.3.0077 .0074 .0040 . MINIMUM CLEARANCES FOR EASY ASSEM3LY. 2 IM m in.0087 .9.0083 0.3H.0243 .0162 . in.2.-H.0293 . allowances.0138 .0060 . in. p.—Tolerances on Buttress threads.'M« . external and internal threads diaofint thread >H«tol 1 tolM lHtoJH 2H to4 4to8_.0114 6.0046 0.0187 .1H.0160 . The allowances for various combinations of pitch and diameter are given in table XIV.0056 .—Illustration of tolerances. However.0135 . 1 Allowance on major.8.0201 .2.0078 .008» .10 11.0068 .0060 .0152 .20.0067 . 29.0220 . see tables XIV.0224 0. ö.2M 2H 2*i.0231 .0053 .0126 .0083 .'M«---H H.0254 0. 4 tpi) A=Basic thread height=0.—In specifying or ordering product.9114 Max minor diameter=D—C—2ä.7412 8.. «-( indicates that internal member (screw) is to pull.l) 6r=Pitch diameter allowance=0.7800 Max minor diameter=D—2A+minor diameter tol. LH indicates a left-hand thread. and in specifications: N Butt=National Buttress form of thread specified in this section. the abbreviation N BUTT.1500 (table XIV. both the lead and pitch should be shown instead of the number of threads per inch.3) Tolerance on major diameter of external and minor diameter of internal thread=0.3) Internal Thread (nut or tapped hole) Basic major diameter=J9=2.= 1. The complete symbol for indicating a particular size of buttress thread shall consist of the nominal I—m Righthand -Class 1 (free) thread '—National Buttress form of thread —Internal member or screw to push —0. the clearance flank will be the leading flank. or gages with Buttress threads. threading tools. 4. The leading flank is the one which.1114 External Thread (screw) Max major diameter=Z?—0=2.1-in.. pitch -Basic major diameter in inches 32 . when the thread is about to be assembled with a mating thread. lead (double thread) 1 £ (.2L (*-N BUTT—1 The following abbreviations and symbols are recommended for use on drawings. tools.005 (table XIV.= 1. it is important to clearly indicate whether the pressure flank (7°) or the clearance flank (45°) is the leading flank. If the thread is multiple start.66271p=0. If a Buttress screw is designed to push.7850 Min major diameter=£>—2A+2A„=2. number of threads per inch. IDENTIFICATION OF LEADING FLANK.9412 Min minor diameter=Z?—2A= 1.0726 Min major diameter=Z?—ö—major diameter tol.l) A.— 1. =lcad. faces the mating thread. pressure flank of thread the leading flank. («indicates that internal member (screw) is to push.N BUTT -1 [_ Right-hand (since designation LH isnotspecified) -Class 1 (free) thread -National Buttress form of thread Internal member or screw to push 1 1 —Threads per inch —Basic major diameter in inches 8<-(NBUTT—2LH I Left-hand —Class 2 (medium) thread -National Buttress form of thread Internal member or screw to pull —Threads per inch Basic major diameter in inches 10—0.=Height of thread in internal thread (nut) and external thread (screw) = 0. no symbol is used to indicate a righthand thread.ik of thread the leading flank.9300 Max pitch diameter=D—A+PD tol.Example: 2.0112 (table XIV. THREAD DESIGNATIONS diameter (basic major diameter of the internal thread).0074 (table XIV.5) Tolerance on pitch diameter of both external and internal thread=0. the symbol indicating whether screw is to push or pull.1p-0.=2.2-in. and finally the class number. Examples: X—20 («. clearance fla.080—4 class 2 Buttress thread (2. and if designed to pull.0676 Max pitch diameter=D-A—0=1.= 1. the pressure flank will be the leading flank on both screw and nut.080 dia.9226 Min pitch diameter=Z?—h—Q— PD tol..=A.0800 Min pitch diameter=Z?-A= 1. = pitch.1657 (table XIV. gages. The clearance flank at 45° will normally clear.5. (2) "not go" thread plug gage having pitch diameter equal to maximum pitch diameter of internal thread. If &»i and 3«2 (in degrees) represent the deviations present in the two flanks (45° and 7°. and the following formula.—(a.) Pitch deviations. The clearance flank at 45° has a greater effect on the pitch diameter measurements than the 7° pressure flank.5. respectively) of a Buttress thread. major diameter 0. measuring the pitch diameter of Buttress thread gages presents some difficulty because of the wide difference between the angle of the pressure flank and the angle of the clearance flank. If the quantities required are small and best sice wires are used to determine the pitch diameter of taps and screws in lieu of thread gages. (4) measurement of pitch by an accepted method. in which the signs are disregarded. (3) measurement of pitch as for external threads. GAGING 1. (5) "go" a-d "not go" plain plug gages for minor diameter. 2.) + tan 7° J inn The values of &Ea obtained by the above formula. (5) measurement of the angles of both flanks either by direct optical projection. and minor diameter equal to minimum minor diameter of internal thread. If excessive clearance (looseness) is objectionable.)Ttan 45' tan (45° ±&*. reading at intervals and over the whole length of engagement. major diameter greater than maximum major diameter of external thread. the corresponding virtual increase in the pitch diameter of the external thread (or decrease for the internal thread) is given by the expression: Virtual change in pitch diameter equals A/i> 2Sp = 1. (3) "not go" thread ring or thread snap gage having pitch diameter equal to minimum pitch diameter of external thread.— A deviation in the pitch of a Buttress thread virtually increases the pitch diameter of an external thread and decreases the pitch diameter of an internal thread. Products that are a snug fit in or on "go" thread gages described below will interchange.35// less than minimum pitch diameter of external thread. RECOMMENDED GAGING PRACTICE. GENERAL. (2) "go" thread ring gage having pitch diameter equal to maximum pitch diameter of external thread. gives values closely approx- 33 . (6) For internal threads: (1) "go" thread plug gage having pitch diameter equal to minimum pitch diameter of internal thread. then the angle of the clearance flank as well as the pressure flank must be held within close limits to secure interchangeable product. and differences in the angles of the clearance flanks of the product is of lesser importance. If &p represents the maximum deviation in the axial displacement (pitch deviation) between any two points on a Buttress thread within the length of engagement.781 ip tan 45°+tan T (b) Flank angle deviations.—Buttress threads are employed for thrust purposes and it is essential to obtain as large a contact area as practicable between the pressure flanks of the threads of mating components. and minor diameter less than minimum minor diameter of internal thread. or by means of suitable templates. This relief should be located so that the shoulders formed at intersection of relief and thread flanks will be approximately equidistant from the pitch line.---(a) For external threads: (1) "go" and "not go" snap or plain ring gages for major diameter. the corresponding virtual change in pitch diameter is given by the following formula: ± tan 7 ±5a T tan7 ( ° ^ ° AEa or P f •° L tan (7° ±Sa4)+ tan 45° ±tan (45° ±««. Therefore differences in the angle of the pressure flanks and of lead in the length of engagement of mating components should be kept as small as possible. therefore the clearance flank angle on thread gages must be held to a tolerance at least as close as the tolerance on the pressure flanks and best size wires should be used. the diametrical clearance space between the assembled product threads will be greater than the minimum clearance (allowance) specified in table XIV. major diameter equal to maximum major diameter of external thread.—A deviation in one or both of the flank angles virtually increases the pitch diameter of an external thread and decreases the pitch diameter of an internal thread.35p greater than maximum pitch diameter of internal thread. PITCH DIAMETER EQUIVALENTS FOR PITCH AND ANGLE DEVIATIONS. (c) Width of root relief: A width of relief at root of p/6 is recommended for "go" plugs and rings and p/4 for "not go" plugs and rings. major diameter greater than maximum major diameter of external thread. and minor diameter 0. do not differ greatly for plus and minus values for 8ati and Sait when Sa{ and da2 arc one degree or less. and minor diameter less than minimum minor diameter of internal thread. 3. If there is any difference in the thread angles or lead of the product and the mated "go" gages used. (4) measurement of the angles of both flanks by optical projection from casts of the thread. However. then the angle of the clearance flank as well as the pressure flank must be held to close limits. 4.4p.0301 .0153 .0930 . 1. However.3.-»/2-0.0818 . 0551 . Height of sharp V thread.2o Height of dedendum »i-0.0800 .0964 .2.0459 .0245 . ' This standard. XIV. iva SECTION XV..4047 . and diameter limits of size for these sizes of lamp base screw shells. 1. candelabra. IB.019 8ctt] where Satt and 6a2 are in degrees or fractions of a degree..0482 .2969 .2023 . 5059 .0241 .1020 .4078 . medium." which was a report of the ASME Committee on Standardization of Special Threads for Fixtures and Fittings. 4 3 2 in.30586p Root radius r-0. receptacles.0445 0.0891 . 6 S . The latest revision should be consulted when referring to this ASA document. or the resulting reduction in depth of engagement has to be limited. in.1000 . and similar devices.0275 .5938 .890»4p Basic height of thread A-0.27544p Crest truncation /-0. instead of the 0.1333 . with the exception of the more recently adopted intermediate size. XIV.5000 .1000 . 0. AMERICAN STANDARD ROLLED THREADS FOR SCREW SHELLS OF ELECTRIC LAMP HOLDERS AND SCREW SHELLS OF UNASSEMBLED LAMP BASES6 The specifications given herein for American Standard rolled threads for screw shells of electric lamp holders and for screw shells of unassembled lamp bases.0201 . has been adopted by the American Standards Association. as shown in figure XV.1635 . THREAD SERIES [\<JURE XIV.2529 . the tolerance on major and minor diameters is the same as the pitch diameter tolerance (for the same class). not included in the British Standard.0253 0.0070 0.0306 0.1012 . threads per inch.2453 . See fig. except that this section includes diameters from }{ to % in.. the tables for pitch diameter tolerances and allowances for sizes over one in.0981 . published by the British Standards Institution.2667 . pitch diameter tolerances for such combinations when required can be determined by use of the diameter and pitch increments given in table XIV.0804 .3) Threads Pitch per inch p II The Buttress thread covered in British Standard 1657:1950 Buttress Threads. The form of thread recommended in the British Standard is shown in figure XIV.1377 .1116 ." by the ASME.0833 .2754 2H m m .0075 . BRITISH STANDARD BUTTRESS THREAD TABLE XIV.0612 . With these exceptions.24S32J» 34 .0843 .6.0506 .6p depth.1836 .0465 . intermediate.4000 .0233 . which is the basis of the thread covered by this section.1227 . and mogul. 20 1« 12 10 8 . which are used on lamp bases.) NOTATION The sizes for which standard dimensions and tolerances have been adopted are designated as follows: "miniature. (Heavy line Indicates basic form.—British Standard form of Buttress thread.0087 .3. which are used in electric sockets. are given in table XV.2000 . and XIV.0409 . In the British Standard.3333 . The American Committee does not consider it advisable to encourage for regular use certain combinations of the larger diameters with fine pitches covered in the British Standard.7125 . and limits of size for lamp holder screw shells.8000 1.2227 .0100 .0172 .3059 .009 a«2+0.1102 . It is published as ASA C81. radii of thread form.0116 .0279 .6667 .2039 .0558 . 1474 of The American Society of Mechanical Engineers entitled "Rolled Threads for Screw Shells of Electric Sockets and Lamp Bases.1529 .0121 .3372 .—Numerical data for British Standard form Buttress thread (Basic depth of thread=0. attachment plugs.0613 .13946p Crest width F-0. in.3 and the numerical data for the British form in table XIV.0344 .0333 . and similar devices.0491 .0421 .4453 .0382 .4000 . Both standards use the same formulas for the pitch diameter tolerances and allowances for the three classes common to both standards. are in agreement with tables XIV. However.0667 .0000 .0400 . 2. are given in table XV.1265 .1113 .2447 .0123 0.1600 . 0500 0.1963 .3563 .6117 .0510 . FORM OF THREAD The thread form is composed of two circular segments tangent to each other and of equal radii. 29 West 39th St.3200 .1781 .0500 .0689 .0557 . in substantially the same form. were originally published in 1915 in Bulletin No.0349 . has a basic depth of thread of OAp. in. The corresponding designations.12055p Root truncation »-»0.-0.0402 .2500 . in.0204 .1223 .0140 . in.0200 0.imating the values obtained by the above formula: &Ea=p [0.1250 .0632 .0151 . in.2000 .Y.0230 . 6.2.0250 . fuse plugs.6. XIV.50586p Height of addendum n.4p Height of external thread (screw) ».0603 .//-o.0025 .1484 .1.0138 .1395 .0765 . "Rolled Threads for Screw Shells of Electric Lamp Holders and for Screw Shells of r nassem bled Lamp Bases.5 in this section. but provision is made for smaller tolerances where the crest surfaces of screw or nut are used as datum surfaces. New York 18.01160 0.1667 .0697 .0742 .1686 .0307 .0918 . 1.4894 . the two standards are in agreement as to the preferred pitch series and the preferred diameter series. dimensions.0316 .0174 .2204 .3. N." The thread designations. 0353 .l.11111 . and a "not go" plain plug gage governing minor diameter are sufficient. 0. 0.ages to govern the major diameter and thread orm. (a) GAGING OF LAMP BASE SCREW SHELLS. and "go" and "not go" plain plug gages to govern minor diameter.050 14 10 9 7 * 680170* 35 .25000 4 in.027 .857 1.020 .445 1 2 3 <n.651 1. 0.470 .0210 . 0.37S .400 . XV.664 1. for control in manufacture. 0. "Not go" thread ring gage.027 .0470 . "go" and "not go" threaded ring gages to govern the minor diameter and thread form.0312 . (2) Inspection gages. minimum thread TABLE "Go" thread plug gage. allowance.591 . 0.3835 .420 .0353 .031 1. 0.07143 . minimum thread size to plus 0.645 1.0906 6 in.—For the final acceptance of the product.370 .1428« .0003 in.—Manufacturing tolerances on inspection or working gages shall be as follows: LAMP BASE SCREW SHELL EXTERNAL THREAD BASE SCREW SHELL FIGURE XV. 0. 0.0908 6 in.610 .477 1 2 3 in.045 1. (2) Inspection gages.971 1.0*0 Miniature lamp base thd OnivW»*»» l»irip b»m» th<\ 14 10 9 7 4 TABLE XV.3435 .2.—American Standard rolled threads for lamp holder screw shells Major diameter Minor diameter Thread designation Threads per inch Pitch Height of thread Radius Minimum Maximum Minimum Maximum 6 in.29000 4 in.025 .0002 in.3375 .597 .10000 .330 . 0.465 9 in. maximum major diameter to minus 0. "go" and "not go" thread plug ?.14286 . (6) GAGING OP LAMP HOLDER SCREW SHELLS.476 . size to plus 0.415 .426 . a "go" thread ring gage governing minor diameter and thread form and a "not go" plain ring gage governing major diameter are sufficient.—For purposes of inspection in the final acceptance of the product.565 7 in.— (1) Working gages.545 8 in. GAOES INTERNAL THREAD LAMP HOLDER SCREW SHELL Gages are necessary to control dimensions in manufacture and to insure interchangeability and proper assembly.— (1) Working gages.0210 . American Standard rolled threads for screw shells of electric lamp holders and lamp bases.053 1.8776 .—For each size of lamp base screw shell there should be provided for control in manufacture.603 .979 1.Ulli .0470 . and "go" and "not go" plain ring gages to govern major diameter.3.020 .033 .l. and tolerances.0002 in.07143 . 0. a "go" thread plug gage governing the major diameter and thread form.577 8 in.10000 . maximum thread size to minus 0. minimum major diameter to plus 0.037 1. (c) TOLERANCES ON GAGES.—Illustration of thread form.410 . LAMP HOLDER SCREW SHELL "Go" thread ring gage.0003 in.455 9 in. "Not go" plain ring gage.—For each size of lamp holder screw shell there should be provided.025 .555 7 in. "Go" plain ring gage.-American Standard rolled threads for lamp base screw shells before assem bly Major diameter Minor diameter Thread designation Threads per Inch Pitch Height of thread Radius Maximum Minimum Maximum Minimum S in.335 .0003 in. 0.0312 .965 1.033 .405 . 0.987 1. 0. (c) Allowances for limited eccentricities so that centralization and squareness of the objective are not influenced by such deviations in manufacture. 389. 487. Final approval as an American Standard was given on January 7. and basic and design dimensions for the threads are given in table XVI. In conformity with comments received. and intended to be interchangeable with. 2. ' This section Is In substantial agreement with American Standards Association publication ASA Bl. 266.—Positive allowances (minimum clearances) are provided on the pitch. Thread check plug for "not go" thread ring gage.0003 in. 1896. p. ALLOWANCES. dated April. 0. The thread is of the single-start type.ll. p. the American Delegation presented ASA Paper Bl/57 and A. p. CHECK GAGES FOR LAMP BASE SCREW SHELL GAGES NOSEPIECE PILOT Thread check plug for "go" thread ring gage. it was recommended that the title of this document be amended to read. The history of this standard is in the Transactions of the Society: 1858. dated October. however.800— 36AMO 7 1. The thread is based on." which is published by the ASME. 1915. 1948. "Microscope Objective Threads.1. New York 18." This thread has become almost universally accepted as the basic standard for microscope objective and nosepiece threads. FORM OF THREAD. 29 w. MICROSCOPE OBJECTIVE AND NOSEPIECE THREADS." On the basis of this proposal a draft of a proposed American Standard. having an included angle of 55° and rounded crests and roots. 175. such modified threads being completely interchangeable with the RMS threads.0002 in. Drawing ED-95 giving limits of size for a truncated Whitworth thread. Since a thread form vith rounded crest is preferred in Great Britain »or optical instruments. 1924.800 in. A typical arrangement is shown in figure XVI. 92. 1859. Experience has established that the principal attributes of a good fit for microscope objective and nosepiece threads are: (a) Adequate clearance to afford protection against binding due to the presence of foreign particles or small thread crest damage."Not go" thread plug gage. p. This section covers the thread used for mounting the microscope objective to the nosepiece. and 36 tpi. maximum minor diameter to minus 0. 1958. which were subsequently used throughout the world. major. was circulated to the Bl Sectional Committee membership for comment.0003 in. Formal recognition. minimum thread size to plus 0.0003 in. N. The need for the above characteristics stems principally from the inherent longevity of optical equipment and the repeated uses to which objectives and nosepiece threads are subjected. p.Y. 1954.. "Proposed Permitted Truncation and Tolerances for RMS Thread. 39. SPECIFICATIONS 1.0002 in. At the Conference on Unification of Engineering Standards held in Ottawa in 1945. formulas. GENERAL AND HISTORICAL OBJECTIVE FIGURE XVI. Because of its British origin. (b) Sufficient depth of thread engagement to assure security in the short lengths of engagement commonly encountered. SECTION XVI. and 1936.—Typical arrangement of microscope objective and nosepiece. pp. based on the Whitworth screw thread system. 1911. by ASA. The standardization of the microscope object« e and nosepiece threads is one of the projects toward unification of screw thread standards among inchusing countries. such as photomicrographic equipment. minimum minor diameter to plus 0. the basic thread possesses the British Standard Whitworth form. the thread introduced and adopted many years ago by the Royal Microscopical Society of Great Britain and generally known as the "RMS thread.—This section covers only one nominal size of thread which has a basic major diameter of 0. 39th St. 230. In Great Britain. The latest revision should be consulted when referring to this ASA document. maximum thread size to minus 0. In practice. Symbols. was approved by Subcommittee No. 1.O. American manufacturers of this thread have always employed modifications of the Whitworth form because of their preference for flat crests. "Go" plain plug gage. the Royal Microscopical Society had established standards for microscope objective threads in 1858. 377. maximum thread size to minus 0. has been extremely limited. a revised draft. "Not go" plain plug gage. 1. p. 2. 36 . 4 on Instrument Screw Threads and subsequently submitted to the Sectional Committee for approval. This thread is recommended also for other optical assemblies of microscopes and associated apparatus. 960491p . This minimum diameter is not controlled by gages but by the form of the threading tool.00205 in.026680 m.2.0018 In.7626 In.» D D. E E.7822 in. LENGTHS OF ENGAGEMENT. PILOT ON OBJECTIVE THREAD. Pitch diameter of external (objective) thread.7626 3 mm 20.—Symbols. 0.0030 7 in.746 » 19.0030 .182 6 in. the value established by the British Royal Microscopical Society in 1924 and now widely regarded as a basic requirement.8000 . tolerances on the internal (nosepiece) thread shall be applied plus from the basic (design) size and tolerances on the external (objective) thread shall be applied minus from its design (maximum material) size.7804 .370 4 in. Minor diameter of external (objective) thread. b 0.520 9 in. >> Allowance (minimum clearance) on pitch diameter is the same as on British RMS thread.800—38 A MO Symbol Basic thread form Formula Dimension Half angle of thread Included angle of thread Pitch Height of fundamental triangle. . D D-2U-0 D-hk D-ht D-In-G D-2ht D-iK D-2kt-0 0. . 0. 800—86A MO External (objective) thread Internal (nosepiece) thread Tolerance 5 mm 20.596 Tolerance 11 in.8092 . 5.243624p . The pitch diameter tolerances for the external and internal thread are the same and include both lead and angle deviations.2. k F. r 1/» 0.—The tolerances specified herein are applicable to lengths of engagement ranging from % to % in.073917p 0. (See fig. The allowance on the pitch diameter is 0.554 19.) XVI. D. 0.<> Minor diameter of internal (nosepiece) thread.7822 In. Lengths of engagement exceeding these limits are seldom employed and.7941 in. 0. Width of flat at crest Width of flat at root Basic truncation of crest from basic Whltworth form..7626 in. Major diameter of external (objective) thread. 3.0038 in. .7804 In. They are derived from the RMS standard of 1924 and are the same as for the current British RMS thread.0068 In.944 19.868 19. (approximately 15 to 50 percent of the basic diameter).0023 in.7852 . it is to be assumed that the threads will be supplied in accordance with the tables in this section. For microscope objective and nosepiece assemblies. .7644 in. nominal and basic.137329p WW MW 36 0.0046 in.7911 . V A»-t/-0. 0. a 2a n P H ft. formulas. .—Limits of size and tolerances. Where interchangeability with product having full-form Whitworth threads is not required the allowances on the major and minor diameters of the external (objective) thread are not necessary.7822 . Design thread form Height of truncated Whltworth thread. The same allowance is also applied on both the major and minor diameters. Major diameter of internal (nosepiece) thread.640327p . . . . and minor diameters of the external (objective) thread. r t?) Diameter Maximum 1 2 in.).0018 in. K K.7685 Minimum 8 mm 20.).027778 In.0157 In. All tolerances are given in table XVI. Basic and design sizes Major diameter.1. Benefits are derived principally from changes in the major diameter where increasing both limits improves the depth of thread engagement. 0. and increasing only the maximum limit grants a larger manufacturing tolerance.7774 «. and basic and design dimensions. a • An allowance equal to that on the pitch diameter is also provided on the major and minor diameters of the external (objective) thread for addition.TABLE XVI.» Fitch diameter of internal (nosepiece) thread. TOLERANCES.170 19. XVI.320 19.7715 Maximum 10 mm 1-20. unless such deviations are specifically covered in purchase negotiations.—In accordance with standard practice.7685 In. Height of baste thread Radius at crest and root of British Standard Whltworth basic thread (not used). E. f. are not provided for in this section. The diameter of the pilot shall not exceed 0.566410p 0. K. The tolerance on the major diameter of the external thread and the tolerance on the minor diameter of the internal thread are the minimum values which experience has demonstrated to be practicable.0178 In.822 19.800 In. 4.7552 Minimum Pitch JO • Extreme minimum minor diameter produced by a new threading tool having a minimum flat of p/12 (=0.166667p . . TABLE since the forms at the root and crest of the truncated internal (nosepiece) thread provide the desired clearances.800 in. the length of engagement most generally employed is % in.: clearance and centralizing. . 37 . 1. . However. .7941 . . . consequently. either both limits or only the maximum limit of the major and minor diameters may be increased by the amount of the allowance. In such cases.094 19. This maximum diameter is not controlled by gages but by the form of the threading tool. . Adequate depth of thread engagement is thereby assured.0014 in. b Extreme maximum major diameter produced by a new threading tool having a minimum flat of p/20 (=0.—A pilot (plain portion) shall be provided at the leading end of the objective thread for ease of assembly with the nosepiece thread. 2. 6.175 mm. Their application is illustrated in figure XVI. See table X VI.INTERNAL THREAD. 3. in specifications.4.800—36AMO. THREAD DESIGNATION.—This thread is to be designated on engineering drawings.—Diaposition of tolerances.2. LIMITS OF SIZE. the length of engagement most generally employed for the American thread is % in. However. 7. allowances. The limits of size of the British thread are given in table XVI. 38 The British and American threads are the same with the following exceptions: The British thread has a basic and design thread form as shown in figure XVI. .—The limits of size for both the external and internal thread are given 'in table XVI.800—36AMO thread.l for Interpretation of symbols.) whereas the lengths of engagement for the American thread may range from % to % in. as given below: 0. BRITISH STANDARD FOR MICROSCOPE OBJECTIVE AND NOSEPIECE THREADS Recommended gage dimensions are listed in table XVI.2.2. (3. The length of thread on the British objective is 0. and on tools and gages by the symbol "AMO" preceded by the basic major diameter in inches and the number of threads per inch. GAGE DIMENSIONS 4. SCREW (OBJECTIVE) FIGURE XVI. NUT (NOSEPIECE) MAJOR DIA EXTERNAL i MAJOR DIA ' EXTERNAL ALLOWANCE OH THREAD TOLERANCE ON THREAD I PITCH DIA ALLOWANCE (EXTERNAL THREAD ONLY) ~ MINOR DIA TOLERANCE ON INTERNAL THREAD EXTERNAL THREAD.3 whereas the American thread has truncated crests and roots as shown in figure XVI.125 in. and crest clearances for 0.3. minimum £.7824 "NOT OO" THREAD PLUG GAGE A.3. Mln— 2*j E.Mln. .7802 . Major diameter.7802 _. Major diameter.Max.0002 "GO" THREAD RING GAGE E.822 .7774 19.0002 In.7852 . minimum Pitch diameter.Mln.7804 .Max.7941 . fl. 7982 20.7644 . E. Max E. E. Max D.7804 .868 0.944 19.7945 .7952 20. Mln "Go" A Plug D.Mln. if. Max. E.0004 _ . Max —0. H/6-0. maximum Pitch diameter. E. Max -0.4.0004 .Min. minimum Et Max "Go" A Plug. minimum Pitch diameter. E.Max. maximum Major diameter. minimum Major diameter. Min +0.. maximum ntch diameter.TABLE XVI. minimum Pitch diameter. E. Min+0. E.16O082P r-0. E.7644 19.7941 . minimum Pitch diameter. Major diameter. Max.7852 .762« 19. D. Mln. maximum I).7774 .8000 .274 0. Max. Min +0. Min.Mln. 0.7776 .. Max E. minimum D.7774 . Max.8000 20. mm in. Mln "Not Oo" A Plug E. Min. Mln+0. maximum D. Max Pitch diameter.7941 . maximum Pitch diameter.0004 F. Min.416 .. Max +p/3 .-.320 . maximum Minor diameter.. 0.7776 "NOT GO" THREAD RING GAGE E. E..7804 19.0002. Mln D. "NOT GO" SETTING THREAD PLUO OAOE (A-NOT GO) D.492 . Max— 0.0002 in. Mln. Mln E.7937 . Max. Mln—p/3 E.. Max "Not Go" A Plug E. E. maximum E. D.7685 INTERNAL (NOSEPIECE) THREAD "GO" THREAD PLUG GAGE D.0004 . 0. E.0004.960491P »-2/3H-0.7681 . mm mm in. minimum Major diameter. 9 Diameter Maximum 2 3 Minimum 4 5 1 Simple effective in.7945 . E. 7674 FIGURE XVI.3. E.—Recommended gage dimensions for microscope objective and nosepiece thread. minimum Minor diameter. Major diameter. 746 mm 19.198 0.0004.0002. 800—36A MO Description EXTERNAL (OBJECTIVE) THREAD Formula Dimension Dimension symbol "GO" SETTING THREAD PLUG GAGE (A-GO) D. minimum Pitch diameter.Mta.7822 19.370 . maximum Major diameter. E. minimum Minor diameter. Tolerance on lead Tolerance on half-angle of thread.8004 ..—Limits of size for the British microscope objective and nosepiece thread External (objective) thread Internal (nosepiece) thread Minimum 6 7 Maximum 8 in. E. 0..—Basic form of Whitworih thread.7640 . Max.640327P 39 .Max. D. Pitch diameter. E. Max D.I37329p H-0. E. D. Max -0. Mln+0. maximum Pitch diameter. maximum Minor diameter. Max -0.MIn E. Mln.7822 . Max. ±0 dcg 20 mln TABLE XVI. maximum Pitch diameter.7850 ±0. —(a) Surveying instrument. The thread dimensions are shown in table XVII.l. levels. DIMENSIONS.—The form of thread profile shall be the American National fonn as shown in appendix 1 of Part I of Handbook H28. 2.—The base plate is that portion of the surveying instrument which contains the thread used for fastening it to the tripod head. See table XVII. GAGE DIMENSIONS In 1927 a manufacturers' subcommittee working with the Division of Simplified Practice of the National Bureau of Standards prepared a specification for a tripod thread having a 60° thread angle and a nominal diameter of 3% inches. 4 on Miniature.3208 4 Is. passed a resolution recommending that this thread be adopted as an American Standard. DEFINITIONS. 3.5000 3.l.SECTION XVII. tolerances. and allowances. 0.0162 . Transits one-minute.l. and transit tripods. This thread was considered suitable for use with transits having horizontal limbs 4J4 inches or more in diameter at the edge of graduation.—The tripod head is that portion of the tripod or other means of support to which the surveying instrument is affixed when in use.3432 3 in. The tripod head and base plate shall be in accordance with the dimensions shown on figure XVII.l. It was considered for adoption as a commercial standard. This threcd Is specified in Federal Specification OQ-T-621.481)4 3. 3.) 2. XVII. 1. 3. 3.—The thread shall have a basic major diameter of Z){ in. and similar types of apparatus most commonly used when mounted on a tripod.l. 0. it does not have this official status at the present time. The dimensions of this thread were first circulated in 1927 as NBS Drawing B-1180. (See fig. FORM OF THREAD.4WM 3 4154 3. in accordance • This section is In substantial agreement with the March IMS proposed draft of the American Standards Association bearing the same title. SURVEYING INSTRUMENT MOUNTING THREADS8 1. on March 6. and Surveying Instrument Threads of ASA Sectional Committee Bl. INTERNAL THREAD (BASE PLATE) EXTERNAL THREAD (TRIPOD HEAD) ALTERNATE DESIGN WITH CHAMFERED THREADS FIOUKE XVII. SPECIFICATIONS Recommended gage dimensions are listed in table XVII.l for thread dimensions. TABLE XVII.—Surveying instrument tripod head and base plate.—This section covers the nominal dimensions and limits of size of the threaded portions of the base plate and the tripod head used for securing a surveying instrument to its tripod or other base of support.3792 Tolerance 8 in.0034 . 2.— The term "surveying instrument" shall be deemed to apply to transits.) (c) Base plate. GENERAL AND HISTORICAL with standard practice the thread designation is: "3^—8 SPECIAL FORM. 0.0034 .0134 Major Pitch Minor 40 .0044 . 3.—As the limits of size and tolerances do not correspond to a standard Unified or American National thread class. Microscope Objective. 60° thread" followed by all limits of size. and 8 threads per inch.4232 3.0145 Diameter Maximum Minimum Tolerance Allowance 5 in. 1958 Subcommittee No. DESIGNATION.(1044 . XVII. and also for all engineers' levels.l.4110 3. 3. However. surveying instrument mounting threads Tripod head (external) thread Hase plate (Internal) thread Minimum ß in. but as all the makers of surveying instruments did not agree to its adoption.0219 1 2 in.2.—Limits of size. (6) Tripod head. 8 threads per inch. SCOPE.4188 3.3647 Maximum 7 in. 1. (See fig. 060 MIN- "Not go" thread ring gage in.3910 3.• FLANGED 1. 42. PH3.266 in Pitch diameter 233 0.—This subsection describes the screw commonly used on American photographic tripods.3?! MIN SOCKET DEPTH RECOMMENDED FOR HEAVY CAMERAS Tolerance on lead: ±0. Inc. 3. 3. RECOMMENDATION FOR HEAVY CAMERAS Major diameter.217 41 . Fin URE XVIII. max. .4110 3.4180 "Go" thread ring gage "Not go" setting thread plug gage in. min Pitch diameter.1876 Min 0.0004 in. min. These standards are published by the American Standards Association.4804 3. Pitch diameter. Including thread dimensions. PH3.—Tri-jod socket in camera.4114 3. long. • It will be noted that the "not go" thread plug gage ia truncated on the major diameter below the corresponding dimension of the "go" plug gage. free from obstructions. HEAVY-DUTY APPLICATIONS. TRIPOD SCREW.S007 3.4188 Major diameter. Minor diameter Mm 0. PII3.340 MAX.12 Attachment Threads for Lens Accessories. Pee p. it is recommended that a spacer be supplied for use with cameras having shallow sockets.6)» 0.23 Shutter Cable Release Tip and Socket With Taper (European) Thread. max Major diameter. 10 It is recognized that some nonstandard tripod screws (probably as a result of plating build-up over threads machined to standard tolerances) have been made oversize.2108 BASE PLATE (INTERNAL) THREAD "Go" thread plug gage "Not go" thread plug in.4736 3. .237 in.4164 34180 3. Minor diameter 211 . min 3. The threads shall be as specified in the preceding paragraph for the tripod socket. See p. For this reason. 42. The dimensions. Where accommodation of such a nonstandard screw has been considered important. in sufficient detail to promote the interchangeability of cameras on tripods. • The material included In this section is in substantial agreement with the following American Standards Association publications: PH3. SCOPE. 2164 . 2. SPACER.l. PH3. This is to insure noninterference of the "not go" gage at the major diameter. The socket shall have %—20 UNC—IB threads in accordance with part I. min.2.4114 3. 2489 in. The latest revisions should be consulted when referring to these ASA documents.2175 196 Max 0. include all plating or other finish. %-in.4184 3. 5. It Is recommended that a clear area. 40th St. -O. See p. 2500 in . 3. the screw and socket specified herein indicate two of many possible general designs.4192 3.4811 3.4232 3. 2248 in. RECOMMENDATION FOR LIGHTWEIGHT CAMERAS 0.t«3 MAX FLANGE THICKNESS . surround the socket In the camera.IST MIN SOCKET DEPTH RECOMMENDED FOR LIGHTWEIGHT CAMERAS 0. The thread dimensions are: Major diameter Pitch diameter.1"—The tripod socket in the camera shall be in accordance with figure XVIII.. The thread dimensions are: Major diameter Pitch diameter Minor diameter Max 0.—The tripod screw shall be in accordance with figure XVIII. 1/4—20 UNC—1A/1B THREADS (PH3. The screw shall h»ve %—20 UNC—IA threads in accordance with part I. 1/4—20 UNC—1A. PHOTOGRAPHIC EQUIPMENT THREADS* 1.—Recommended gage dimensions for surveying instrument mounting threads TRIPOD HEAD (EXTERNAL) THREAD "Go" setting thread plug «age fn. 48. sockets have been produced to the following dimensions: Min Max Major diameter 0.6 Tripod Connections for American Cameras H-lncb-20 thread. and the corresponding threaded socket in cameras.4729 3.4228 3.340 in.5000 3. Pitch diameter.7 Tripod Connections for Heavy-Duty or European Cameras H-inch-16 Thread with Adapter for M-lnch-20Tripod Screws.Y.24 Shutter Cable Release Tip and Socket With Straight (American) Thread. it is recommended that the tripod connections shown in the following subsection be used. in diameter.2. PH3. at least 2 In. 111—SO UJC—1B. 42. 0.4966 3.10 Threads for Attaching Mounted Lenses to Photographic Equipment. 10 E.. 1. Bee p. max Major diameter.2.3647 3. 3. The spacer shall be in accordance with figure XVIII.TABLE XVIT. The dimensions. section III. Tolerance on half-angle of thread: ±0° 6 min. See p. 48.. in. Including thread dimensions.3. 3.IT5 MAX. See above. section III.050 MAX DEPTH IF COUNTERBORED CR COUNTERSUNK O. New York 16.3640 The undercut in the tripod top around the base of the screw provides clearance for the flange found around the tripod socket in some cameras. TRIPOD SOCKET IN CAMERA. 207 4.—Tripod screw. SECTION XVIII. Include all plating or other finish.4989 3. N.4110 0. 2367 in.—On tripods having a screw 0.—For heavvduty applications.3917 FIOURE XVITI. It is not intended to prescribe design except for the dimensions affecting interchangeability. TRIPOD CONNECTIONS FOR AMERICAN CAMERAS. 1/4—20 UNC—IB. include all plating or other finish.165 ±0. SCOPE. Include all plating or other finish. THREAD FORM. Including thread dimensions. 318—16 UNC—1A external thread. O. .—The tripod socket in the camera shall be in accordance with figure XVIII.12«) 4. The screw shall have %—16 UNC—1A threads in accordance with part I. a threaded bushing as shown in figure XVIII. 3750 in. including thread dimensions.—This subsection consists of the specifications for the threads used for attaching mounted lenses to photographic equipment. . page 41. ADAPTER. TOLERANCES.—Spacer for use on tripod with O.1.010 FIGURE XVIII.SiO-in. surround the socket in the camera.2970 O. camera. mended. see footnote a to the table.5. 3 18—16 It Is recommended that a clear area.3266 FIGURE XVIII.307 Max 0. The thread dimensions are: Major diameter Pitch diameter Minor diameter Max 0. for example. Min 0. 4. In diameter.—This subsection consists of the specifications for the attachment threads for lens accessories. SCOPE. SCOPE. and lengths of the threads in common usage for attaching mounted lenses to photographic equipment are listed in table XVIII. f. The bushing shall have a %—16 UNC—1A external thread as specified in paragraph 2 of this subsection and a %—20 UNC—IB internal thread as specified in paragraph 3 of subsection 1.O5O MAX 4-0. For this reason. above. LIMITS OP SIZE. .TOP 0. It is not intended to prescribe design except for the dimensions effecting interchangeability. 3344 . The dimensions given in this table are not intended to preclude the use of threads specified by the Royal Microscopical Society.6 is recom42 1. The lens accessories have an external thread which mates with an internal thread in the lens mount. For the dimensions of the %—20 tripod screws and sockets used on American cameras. 3. 3429 in. 2.10») 0. The socket shall have %—16 UNC—IB threads in accordance with part I.5. 3/8—16 UNC—1A/1B THREADS (PH3.—The Unified form of thread profile as specified in section III.—To adapt a tripod having a screw with a %—20 UNC—1A thread as specified in subsection 1. the corresponding threaded socket in cameras. Include all plating or other finish. for attaching lens barrels to lens boards as in the case where flanges are employed. The dimensions.060 MIN 0. and the bushing to adapt American tripods to European cameras. in sufficient detail to promote the interchangeability of cameras on tripods.—Tripod socket in UNC—IB.OSO MAX DEPTH IF COUNTERBORED OR COUNTERSUNK The outside diameter of the spacer shall conform to that of the tripod head. Including thread dimensions. THREADS FOR ATTACHING MOUNTED LENSES TO PHOTOGRAPHIC EQUIPMENT (PH3.—The limits of size. tolerances. shall be used. 1/4—20 UNC—IB internal thread. AND LENGTHS OP THREADS. 3331 . 2. part I. TRIPOD SOCKET IN CAMERA. . The thread dimensions are: Major diameter Pitch diameter Minor diameter A/in 0.3. 818—16 UNC—1A The undercut In the tripod top around the base of the screw provides clearance for the flange found around the tripod socket In some cameras The dimensions. see subsection 1 on page 41. free from obstructions.OAS MAX FLANGE THICKNESS IF FLANCEO FIGURE XVIII. the screw and socket specified herein indicate two of many possible general designs. section III. Section III. TRIPOD CONNECTIONS FOR EUROPEAN CAMERAS (HEAVY-DUTY APPLICATIONS).4 — Tripod screw. ATTACHMENT THREADS FOR LENS ACCESSORIES (PH3.000 -0.7») 1.—The tripod screw snail be in accordance with figure XVIII.3595 in. 1. TRIPOD SCREW.t least 2 In.—This subsection describes the screw used on some European photographic tripods.6. 3. 2.321 1. 5. The dimensions. 3737 in.— Adapter. length screw. to a camera having a tripod socket with a %—16 UNC—IB thread. For sizes larger than shown in table XVIII. 3.005 FIGURE XVIII.4. 0.0036 .2084 2.5000 .6989 2.7500 3.8520 .156 ..156 .8750 1.0941 1.7500 3.9928 2. • These are standard sizes of the Unified 32-thread series as given In tables 1 and 2.2229 2.187 .0028 .0000 2.0867 1. 0.7270 .4744 .2297 1.250 . or other finish.0045 .TABLE XVIII.156 .7297 1. 0.9684 3.4865 .4693 2.0048 w^9 14 in. 0. 1*4-32 2-24 2V4-24 2H-24 234-24 3-24 3H-24 » Larger sizes than she sra in the table may be specified by increments of H in.1250 1.0035 .4729 2.8469 .5000 2.4894 .1084 1.3750 1.7193 2.2194 2.9692 3. 9774 2.4729 Max 11 in.13 of part I.2500 1.4729 Min 5 in.0912 1.7500 2.2274 2.250 .0028 .4767 1.9719 1..0035 .4584 Min 10 in.187 .8547 . The standard designation for these is "UN. and lengths of threads for threads for attaching mounted lenses to photographic equipment.7229 2.2428 2. lacquer.047 1.0037 .4836 1.5910 .7440 1. 0.3750 1.7500 .4489 Min 8 in.3547 1.4662 1.2049 2.1019 1.9660 1.3585 1.0046 . such larger sites to have 24 threads per inch. 0.2117 1.0039 .1-1960.9940 1.0040 . 3Ab Nominal size and threads per inch Major diameter Fitch diameter Minor diameter Minor diameter Internal thread.0046 .9777 3.. or other finish.218 .1989 2. 4617 1.7428 2.5000 1.2500 1.2500 2.2440 1.7297 1.7297 . 3367 1.0000 1.5969 .187 .4692 Tolerance Max 7 in.3412 1.160 .1.0038 .6250 .0029 .4489 2.4795 .0038 .0031 .0022 .5000 .5867 . 4797 1.3518 1.2297 1.000U 1. The limits of size are to include plating.7337 1.4865 . 0.0027 .5000 6 in.0045 .0037 12 in.187 ." 43 .4940 1. lacquer.9617 1.7333 .115 . 0.6047 .0037 .9797 1.9584 2.5000 Min 3 in.4549 Max 9 in.6190 .7266 1.0000 3.8750 1.7117 .1047 1.1250 1..6020 .7500 .7219 .9769 1. 0. A (Seesketch) Max 1 2 in.4584 2.9489 2.218 .8547 . 0.. UNS * —Iwv Exterml thread.375 ^-48 H-32« ^-32« #-32« 1-32« 1H-32 1H-32 1H-32 _ 1M-32.218 .7084 2.9729 3.4774 .0000 2.9797 1.4797 1.9729 2.1190 1.5000 1. t> Values shown are based on table IV.9729 3.7049 2.8367 . 0. 3B ■> Pitch diameter Major diameter Maximum length from shoulder to end of external thread.0027 .4778 Tolerance Min 13 ii. 0.8690 .4928 Max 4 in.3547 1.9694 2.5000 2.4549 2.7440 .0035 .0030 .8410 .7297 .9549 3.13 of part I (class 3A/3B threads).250 .0037 . Limits of size and tolerances for these larger sizes are to !• t calculated in accordance with table IV.4843 .6082 .2500 2. 0.7275 2.6250 . tolerances.9549 2.9928 3.4928 2.4691 1.3690 1.2229 2.4729 2.9729 2.2335 1.0036 .3441 1.9834 1. classes 8A/3B.7117 1.0000 3. 7191 1. 2162 1.002« .0027 .—Limite of size.0036 . The limits of size arc to include plating.0036 .6047 .4955 .8583 .7500 2.2268 1. 2191 1.7229 2.1 of ASA Bl.7162 1.0029 .9489 3.7160 .4775 2. 1673 ±0. The length of the threaded portion of the lens accessory.) for larger sizes.9252 1.0 34.5 67. LENGTH OP THREADS. and undercut of attachment threads for lens accessories.3 5.10 mm (0. dimension A.4724 .0 31.9094 2.2. TABLE 'JNDERCUT.846 87.5 36.027778 in.—All threads covered by this subsection shall have a pitch of 0.7677 . and 4.004 In.2 and XVIII.705555 mm (0.5 45.5 25.0433 1.0 in.7.25 ±0.0 32.5 48.) In diameter. etc.7913 in.8071 . 3.346 54.8661 .346 66.30 MM ft).75 ±0.—Length.3583 1. shall be used. part I.5 20. 1. 0.0 mm (0.4252 ■ Series Is that specified by American Standard specification PH3.) are to be by Increments of 5.5 30. This is equivalent to 36 tpi.3.0 28.5 33.—The American Nationa1 thread form as specified in appendix 1. PITCH.4961 1.0 18.7459 2. 0. An example of the thread designation is as follows: 0.5 38.6496 . 0. It MM I0. • Larger sizes (62.—Basic major diameters cf threads for retaining rings for series designation of ülters * Seriäs designation IV V VI VII VIII IX Major diameter mm 23.9843 1.0 13.1969 in.—The basic major diameters for these threads are shown in tables XVIII.7 for the length of the threaded portion of the lens accessory.0 mm.5906 .0276 2.5551 Secondary standard mm 12. 0512 IN. the length of the pilot.004 In.5 22. and the undercut of the thread.).5 26. 7913 1.5 39.—See figure XVIII.5 mm (1.3189 1.1811 1.5 54.6732 1.346 44.7087 . THREAD FORM.5315 .5 33. 2441 TABLE XVIII.4370 1. 4.5 51. XVIII.: 42.0 23.).1396 2.5906-36 NS-2. 3128 1. pilot. 67.10 mm (0.17.0 mm.0 in.1024 1. 2795 1. I.) MA» *— PILOT.9252 1. THREAD SIZE.2.1457 2. shall be 4.0 19.) MAX FIGURE XVIII.) for all sizes up to and including 45.1870 ±0.—Basic major diameters of threads • Preferred standard mm 15.6317 3. u .5 in.5 16. Photographic Filter Sizes.04X IN.2205 1. The thread shall be 50 tpi and shall be adapted for taper tolerances that are the same as for a class 2.8 and XVIII. 0.—For the thread specifications of the shutter cable release tip and socket with taper (European) thread.—Thread details for shutter cable release tip and socket with taper {European) thread {50 tpi). THREAD.9. see subsection 5 immediately preceding this subsection.ll. Multiple thread milling cutters and ground thread taps should not be specified for modified square threads of steep lead angle without consulting the cutting tool manufacturer. a basic thickness of 0.23») O. The angle between the flanks of the thread is 10°.—The American National thread form as specified in part I of Handbook H28 shall be used. 60° STUB THREADS " ±0.10 and XvTII. -* FIGURE i XVIII. Basic dimensions of the 60° stub thread are given in table XIX.11. 10° thread. for example: "l%—6 SPECIAL FORM.24») 1. 45 .055 MIN FIGURE XVIII.5.125)— 44 NF-2 in accordance with part I of Handbook H28.—Shutter cable release tip with straight {American) thread. and are symmetrical about a line perpendicular to the axis of the external thread.9.50p. 60° thread. In accordance with standard practice this thread is designated as follows. a basic thread thickness of 0. SCOPE. ■0. 1.50p." followed by all limits of size. have a basic height of 0.OI! MAX jCHAMFER FIGURE XVIII.50p.—Open type shutter cable socket with straight {American) thread.8. The angle of 10° results in a thread which is the equivalent of a "square thread" in so far as all practical considerations are concerned. see subsection 6 immediately following. 2.—Shutter cable release tip with taper {European) thread {50 tpi). and yet is capable of economical production. for example: "1%—9 SPECIAL FORM. 2.433p.002 1. SECTION XIX. MODIFIED SQUARE THREADS 6. THREAD. MISCELLANEOUS THREADS 1. SHUTTER CABLE RELEASE TIP AND SOCKET WITH TAPER (EUROPEAN) THREAD (PH3.—For the thread specifications of the shutter cable release tip and socket with straight (American) thread. and are symmetrical about a line perpendicular to the axis of the screw.004 Wh. 3. The thread dimensions are shown in figures XVIII. 5(. The thread dimensions are shown on figures XVIII.068 ± 0.015 »AX CHAMFER FIGURE XVIII.—The thread shall be No. The angle between the flanks of the thread is 60°. SHUTTER CABLE RELEASE TIP AND SOCKET WITH STRAIGHT (AMERICAN) THREAD (PH3. SHUTTER CABLE RELEASE TIP AND SOCKET WITH TAPER (EUROPEAN) THREAD.10. The threads are truncated top and bottom. 3. This thread form is illustrated in figure XIX.—This subsection consists of the thread specifications for the shutter cable release tip and socket with straight (American) thread. In accordance with standard practice this thread is designated as follows. 2.OSO ± 0." followed by all limits of size. O. 1. SHUTTER CABLE RELEASE TIP AND SOCKET WITH STRAIGHT (AMERICAN) THREAD. have a basic height of 0. The threads are truncated top and bottom.—This subsection consists of the thread specifications for the shutter cable release tip and socket with taper (European) thread.003 0. SCOPE. Ftf-0.0208 .1083 4 in.0278 .0313 .0252 .0866 .0417 . These are Acme threads. basic proportions.1000 . tiius avoiding Interference with threads of mating parts at minor or major diameters.0284 ..0625 . including standard thread profiles and pitches.0283 .0647 .5p Width of flat at Crest of Root of screw screw (basic).. for bottles and jars are presented on drawings available from the Glass Container Manufacturers Institute.0755 .0357 . thus avoiding Interference with threads of mating part at nririor or major diameters.0250 .0722 .0142 .l.0227 . 1145 19th St. (Bat at root of thread)-0. Washington 6.5p+clearance t (thickness of thread) -0. 0.W.0566 . N.0324 . The amount of this clearance must be determined from the application of the thread assembly.0309 .07143 .5p F..0156 .433p (»+ 0.1.14286 .—Modified square thread (10° included angle).0833 . Inc.20000 .0378 .06250 .0433 . THREADS FOR DAIRY SANITARY FITTINGS Drawings showing threaded "3A" standard sanitary fittings for dairy applications are available from the Dairy Industries Supply Association.0906 .0162 . ««pitch in Inches h (basic height of thread) -0.—Basic dimensions of 60° stub threads EXTERNAL THREAD (SCREW) INTERNAL THREAD (NUT) FIGURE XIX.1133 5 in.08333 . TABLE (INTERNAL THREAD (NUT) Xs . p (basic).0567 1 2 (n.5p H (total height of thread) =0. »-0.061» . 0.0503 .0378 .0357 .—A clearance should be added to A to produce extra height.0313 .0556 .0481 .4563p-0.11111 .02p) Thread thickness (basic).*D.12500 . GLASS BOTTLE AND JAR THREADS Industry standard glass finishes. 46 . 0. thread. N.0180 .16667 . 0625 7 in. Threads per inch Height Total » of thread height of Pitch.02p is added to A to produce extra height. 0.17Xclearance F (basic width of flat at crest of thread)-0.0179 .0361 .. 8 tpi. D.0454 .3.0417 .0453 .227p 6 in.W.0271 . 4.C. Washington 6.0714 .4563p NOTE..0500 .10000 .0500 . 1625 K St.C. 0.250p 0.CU'4M*Cf (SCI NOW CLOUUNCe (see More) XIX.25000 3 In. 0.1250 « 8 7 S 5 4 16 14 12 10 • A clearance of at least 0. r-0.0541 .0324 . ance between bolt heads or nuts and jaws of wrench Wrench openings Min.012 .0000 2.01» . 4 No.875 4.APPENDIX 10.4375 2.008 . 0.026 5.786 .850 71.008 . 0.01» . 5 and No.025 .024 .838 1. Nuts Nominal sin of wrench.375 1.782 3.277 2.006 1.162 3.100 .132 1. WRENCH OPENINGS TABLE 10.446 .157 Tol.014 .625 5.004 .8125 1. 1 in..014 .250 4.183 .hex head bex slotted cap »crews 8 in.028 .3438 8.250 5 376 6.030 . hex.288 .2300 i 8125 1.1873 .000 152.602 .573 .025 .016 .338 34.038 47.540 3.002 .013 .880 4.018 .003 .005 .05 M Me M M Me M He M He M M Me H Me M Ms • M M Me M He M Me M M Me M He M Ms M Ms H H M 1 '"Hi" We H M M M M M M 1 H M M 1 IK IM H H M H M 1 M M 1 IM IN 1H M l IM 1M 1M IM IM IN IM 2 2M 2M 2N 3 % 1 IM IK IM IM IM IM IN IM 2 2M 2M 2M 1 IM IM 1H IN IK 2 m IM IK IM IK 1M IM IM IM 1H 1M IK IK l» IN 1M 2 2M 2M 2M 3 3M 3M 3M 3M 3* 4 4 2M 2M 2H 3 2 2M 2M 3 6. 8 in.008 .252 .220 .5625 2. No.006 .394 1. "Square and Hexagon Bolts and Nuts. 29 w.384 .00» .845 2.017 .027 . Ml fie Ms H •is «• ■Hi M He M Ms M >H» M 'Me H »Me 1 lMe IM IM lMe 1H IM« 1H IM I'M« I'M« lji 2 2Me 2Ma 2M 2H 2Me 2Mt 2H 2M 2>M« 2'Me 3 8M 3M 3M 3M 3H 4M 4M 4M 4M 4M 5 8M SH 5H Mi 6 6M in.7500 2. 47 .6250 2.448 1.862 46.008 .85 11430 117.007 .010 .383 1.257 .010 .125 3.1230 1.827 2054 3."5 1.646 1.023 .012 .0823 1.6250 1.434 3.283 .002 .023 .562 57.378 .225 23.467 1.1.375 31.011 . 6 No.500 3.834 1.) This standard is in general agreement with Appendix 1 of American Standaru A 8A B18.008 \V +0.888 .7500 .0000 1.013 .002 .82 127. 4 in. (W equals nominal site of wrench.500 4.466 2593 2686 2.088 66. 8 No.018 Mai.331 1. semi-fin.62» .731 ■ 3730 ».112 .017 .012 .414 3. Y.022 .019 .015 . 9 in.4375 11.48 123. Tolerance on wrench opening-plus (0.023 .031 6.64» 4.02» .C60 i.011 .122 .022 .350 7.770 3.0625 2. square.008 . also basic or mailmnm width across fiats of bolt and screw heads and nuts Allow.012 .015 1. regular hex.347 .011 .250 08.277 5.004 .8875 .875 17.005 .308 1. 0.015 .273 42.885 2011 2. New York 18. bolts.404 2. square Machine screw 6 in." published by The American Society of yei*«niml Engineers.326 61.953 1.015 .005 .034 .005 .006 .3823 .3125 7.78 107.00» .8750 .812 23.002 . hex-Jam.006 .033 .287 13.3000 .316 .310 .307 8.440 .38 • Regular square only.550 4.020 . 12 and M Ms No.006 .028 .011 .725 88.000 6.003 .686 8.8375 1.007 .007 .00» . .636 . 375 85. hex-Jam.388 65. semi-fin.036 6.576 263» 2. and hexslotted Lag bolts.225 .13 136.8125 .010 .032 .050 20.068 1.297 4.730 12. semi-fin.144 2 in.1875 2.818 .3750 2.055 8.320 1.8126 2.928 8.813 6. hex-Jam.001 .158 .826 . 0.837 22. hex. finished and hex.018 .8230 .880 . 10 .008 .195 .403 3654 3.020 .008 . 11 in. hex.000 3.88 146.482 10.00» .612 76.018 . 10 No.700 14.018 3.89» .200 7».012 65.006 . hex-thick slotted. hexslotted.014 . 3 No.077 1.2187 .027 .147 4.002 .822 1.900 6.006 .768 2. hex. hex-Jam.008 . square Set screws.SO0U 1.»44 1.172 4.900 »6.032 3 in.708 1. No.020 .003 .012 .805 4. 7 in.625 50.004 bom minimum).2812 mm 3. hex.625 4. hex-thick.2.021 .820 1. Wrenches shall be marked with the "Nominal site of wrench" which is equal to the basic or maximum width across flats of the corresponding bolt bead or nut.62 142.013 .016 .011 . 10 in.763 . 325 .425 104.074 2200 2262 2388 2450 2. N.001).006 W+0. 12 in.898 2025 2088 2215 2.026 .8750 2.008 .014 .67« 4. 2 and No.750 3.02» .007 . semi-fin.123 4.142 3.004 .973 3.007 .0375 3.837 .876 6.312 38.192 Finished bei.017 .022 .400 28.142 1 287 1.00 133.606 1. 12 M «6 13 in.272 4.011 .010 .6875 1.438 74. bolts.100 41. hex.008 .676 69.008 .017 .2900 .011 .780 6.—Standard wrench openings Nuts Bolts and screws Finished Heavy and Heavy square.125 133.524 4.783 2.257 1. Allowance (minimum clearance) between m»«immn width across flats of nut or bolt bead and Jaws of wrench equals (1.793 3.618 3.504 .024 .40 9.750 33.150 60.800 52.533 8.008 .0163 .005 . and hexcastle Regular square.666 .016 . and hex-Jam.035 3.036 .393 3.4b.1532 . The latest revision should be consulted when referring to such standards. 10 No.010 .016 .025 36.918 4. bex.014 . 19th St.009 .2500 2.001 .088 28. galling. The American Society of Mechanical Engineers. the maximum torques establish a limit below which seizing. _ (c) Workmanship—Studs should be free from excessive nicks. or both. however. "Shouldering. resulting in either an increase of the external thread major diameter. (2) During driving. are satisfactory. TRIAL AMERICAN STANDARD 1. and field study.1 for conditions of fit. and abnormally high and erratic driving torques. NC5 ONF—For driving in other nonferrous material (nonferrous materials other than copper alloys). 11. Ohio. any hardness. loosening or breakage of externally threaded members has been all too frequent.3. and 11. 2. 10 of ASA Sectional Com* mittee Bl on the Standardization and Unification of Screw Threads. 2. DESIGN AND APPLICATION DATA Following are conditions of usage and inspection on which satisfactory application of products made to dimensions in tables 11. (3) Relieving the external thread major diameter and the internal thread minor diameter to make allowance for plastic flow eliminates the main causes of seizing. a thread micrometer.—Points of externally threaded components should be chamfered or otherwise" reduced to a diameter below the minimum minor diameter of the thread. and pitch diameter limits in tables 11. or both. These torque limits are the same as those in H28(1944) and the 1950 Supplement. Obviously.—(a) Inspection. "Bottoming. these threads are designated class 5. STUD MATERIALS. plastic movement of material. As application experience is gained by users of this < Tbis trial standard is identical in all technical features with the current draft standard developed by Subcommittee No.APPENDIX 11. 2. SAE grades 1.Y. in spite of restrictive tolerance. INTRODUCTION Interference-fit threads are threads in which the externally threaded member is larger than the internallythreaded member when both members are in a free state and which." which is the practice of driving the stud until the thread runout engages with the top threads of the hole. but torques soon become practically constant and increase little._ when assembled. it is desirable to work with greater interferences. They also established minimum and maximum torque values. for uniformity of driving torques. (8) Driving torque increases directly with turns of engagement.) (5) Lubricating only the internal thread results in more uniform torques than lubricating only the external thread and is almost as beneficial as lubricating both external and internal threads. See figure 11. galling or torsional failure of the externally threaded components is unlikely. 11. or thread snap gages having anvils that are not affected by lead or angle. By custom. This results in erratic variations in free stud length after driving. become the same size and develop a high resistance to any applied unscrewing torque through elastic compression. The standards previously published in this handbook were helpful in stabilizing design. or other extraneous material before driving. and 11. with increases of interference. sizes yA to 1% in. (For thin wall applications. grit. NC5 CSF —For driving in copper alloy and soft ferrous material of 160 BHN or less. ASTM A-325 (SAE grade 5) or better. N. thus inviting failure in torsional shear. (c) Trial class 5 internal threads are designated as follows: NC5 IF —Entire ferrous material range. case-carburized studs and unheattreated medium-carbon steel studs.1. and represents the first attempt to establish an American standard for interference fit threads. with copy to Standards Department. The minimum torques are intended to be sufficient to ensure that externally threaded members will not loosen in service. plastic flow of materials occurs. It is predicated on the following conclusions which have been drawn from the research and field experience: (1) Materials of the external and internal interference fit threads compress elastically during assembly and when assembled. (In driving studs. or a decrease in the internal thread minor diameter.3 are predicated.2. (7) Comparatively large pitch diameter interferences can be tolerated provided that the external thread major diameter and internal thread minor diameter are adequately relieved. W thread setting plugs shall be used for all gages. 1. and proper lubrication is used during assembly. THREAD DESIGNATIONS. torques increase directly as the pitch diameter interference for low interferences. chips.-—The length of engagement. NC5 INF—Entire nonferrous material range. (o) Points. The maximum major diameter of the truncated portion of the truncated setting plug should be equal to the minimum major diameter of the stud thread. good or bad. In many applications. 1517 Terminal Tower. 3.—Since angle and lead deviations are not as critical factors as in free fitting screw threads. SAE grade 4. but their use is not primarily recommended. and 8 may be desirable under 48 . 3. the validity of which has been generally accepted in service for the past 20 years.3 are designed to produce adequate torque conditions when heat-treated medium-carbon steel studs.) (9) Studs should be driven to a predetermined depth.2. (4) Such reliefs require an increase in the pitch diameter interference in order to obtain driving torques within the range previously established. Future adjustments to the standard will be based largely on such field reports. It also distinguishes between external and internal Trial American Standard class 5 threads. burrs. and tolerances shall be applied within the product limits. creates radial compressive stresses and upward bulging of the material at the top of the hole. STUDS. or copper plated. "Bottoming" or "shouldering" should be avoided. standard. New York 18. depth of thread engagement. are used. be reported to the Industrial Fasteners Institute. Cleveland. the controlling element for class 5 threaded products is pitch diameter. it was found that the minimum driving torque should be about 50 percent of the torque required to break loose a properly tightened nut. This element can be satisfactorily checked by an optical comparator." which is engagement of the threads of the stud with the incomplete threads at the bottom of a shallow drilled and tapped hole causes the stud to stop suddenly. (6) Trial class 5 external threads are designated as follows: NC5 HF —For driving in hard ferrous material of hardness over 160 BHN. For rapid and convenient control in mass production. Ring gages may be used. testing. The "not go" ring gage shall stop at 1% turns or less engagement in order to maintain minimum pitch diameter interference.—(a) The following thread designations provide a means of distinguishing the Trial American Standard class 5 threads of this standard from the tentative class 5 and alternate class 5 threads specified previously in Handbook H28. limits are applicable before plating. it is urged that results. CLASS 5 INTERFERENCEFIT THREADS. 29 West 39th Street. the use of "go" and "not go" snap gages is recommended. it may be desirable to use longer engagement rather than large pitch diameter interference to obtain desired driving torque. If the threads are zinc. This trial standard' is based on 10 years of research.1. cadmium. if at all. SCOPE This trial standard ' provides dimensional tables for external and internal interference fit (class 5) threads of modified Unified form in the coarse thread series. (6) For threads having truncated profile. It is intended that designs conforming with this standard will provide adequate torque conditions which fall within the limits shown in tabie 11. MAX MATERIAL STUO (LAMEST STUO) MAX MATERIAL TAPPEO HOLE (SMALLEST TAPPEO HOLE) —MIN PITCH 01* —MIN MINOR OIA MAX MAJOR DiA MM PITCH OIA MINOR 01» loctHM ram» MAXIMUM INTERFERENCE INTERNAL THREAD MIN MATERIAL STUO (SMALLEST STUO) MIN MATERIAL TAPPED HOLE (LARGEST TAPPEO HOLE) MAX PITCH OIA MAX MINOR OIA MINIMUM INTERFERENCE FIGURE 11. 49 .—Illustrations showing maximum and minimum interferences. dass 5 threads.1. 9835 1.4584 .5460 .4305 .6111 .5111111 *%* »M« 'Ma 16.8095 .307 .—Limits of size.3680 1. 0.4920 .472 .527 .6195 . 0. TABLK 11.7350 .991 1. 0.5625 .2408 . M«-H H-1S.678 .116 1.M«-18 M-M-.095 1. 1H-6-.5580 .2829 .252 .9640 1. cut.3750 .9727 1.341 1..195 1.497 .544 .1656 1. cut.3917 • This table is based on externally threaded members being steel ASTM A-325 (SAE grade 6) or better.374 .1877 1.2470 .970 1.6378 .7440 . . in.2230 .3680 1.4950 .338 '%* .6895 .125 1. 0.8685 .661 .6111 .3626 .3020 . 1M-6.7360 .8144 .3080 .0465 1.3030 .000 1.321 .5702 .655 .1715 1. class 6* Major diameter Blies and threads per inch NCS HF for driving In NCS C8F for driving ferrous material with in brass and ferrous hardness greater than material with hardness equal to or less than 160 Bhn. 0.4876 .3690 .2794 .431 . 0.4330 12.5176 ..3646 .252 .7503 .-\M dia 160 Bhn. 0.320 in.2768 1.6955 .789 . class 6* NC5 INF Nonferrous material Minor diameter Min Max Fitch diameter Major diameter NCS IF Ferrous material Sizes and threads per inch Minor diameter Min Max Tap drill Tap drill Min Max Min 10 M-20.321 .3579 .1180 1.440 >M« in.2500 1.3053 .2839 1.4846 . 0.5000 M-»~.6195 .4930 in.3991 .1631 1. 0.5495 .0890 1.356 1. We-12 M-ll..265 .4258 . 0.5660 .3125 .642 .2470 .1062 1.213 1.7350 . W-»~1-8..890 1.4258 ..2738 1. 0.372 11.2408 .3030 .2667 1.554 .3710 .3382 . M-10- in.0381 1.228 1. It Is for rolled. L.9262 1.220 1..4695 .904 1.4233 .0000 1.TABLE 11.4788 in..2175 . O 0 H in..5580 .2500 . 1M-7.3414 . M«-12 M-ll .232 1.3911 .7440 .372 .0mm 0.354 in.4089 in.467 In. or ground threads..8077 .265 .—Limit» of size.481 in.4140 .3090 .1.3988 1-8. 50 .4788 in.3538 1.6910 . design form Minor diameter Max Min Max Min Max 10 W-20.1062 1.4500 .8587 .6850 in.8600 .2799 .6250 .485 .196 . ?<«-18 M-16.9827 1.3750 1.3710 .2204 .196 .0322 1.5233 .2312 1.2408 . external threads.9935 1.429 '«i in. 0.3127 • This table is based on externally threaded members being steel ASTM A-325 (SAE grade 5) or better. 1M-7.3344 .1180 1.016 1.1250 1.4950 .2201 .4018 in.0406 1.5000 .0952 1..9242 1.540 .307 . 0. L.9827 1.381 . 1W-7.4330 .6140 . 1H-«-. 1M-6.. internal threads.7270 .1932 . «-10. It is for rolled.3538 1.206 .3090 .2.9935 1.4375 .8502 .4537 in.140 1.755 .247 1.417 .2430 1.-2H dia Pitch diameter. IM I'M« 1»M« «M« VA* I'M« I'M« H 1.2764 .488 .5758 . or ground threads.5mm »M« «M« »Ma »M« 1 .206 .2430 1.7600 .5840 .3965 .4876 .8594 . L.2312 1.3376 . 0.3646 .5124 . 0. 1M-7-.777 .6056 .-lJi dia Max Min Max Min NC5 ONF for driving in nonferrous except brass (any hardness).360 .865 .770 . 0.5136 .8750 1. Q O U in.5495 .4930 in.9316 1.8587 .4330 .2508 .1070 1.3947 .5084 .4547 . M«-14.1572 1.5716 .2470 . «-13. (c) Where sealing is involved. Some opinion has been advanced that careful selection and control of driving speed is desirable to obtain optimum results with various combinations of surface hardness and roughness.certain nonunion». (6) Countersinks. brass or similar materials. in. In applying it to the hole. or other foreign material before driving studs.° T» mln * M-ao.000 +.—Torques increase directly as the length of engagement.0065 . that is be reduced in driving. LEAD AND ANALE DEVIATIONS. i ms inai sianuaru is not mienaeu to cover the use of studs made of stainless steel.192 IM .312 w. 2M +. American research indicates that this increase is proportionately more rapid as size increases.0018 .0128 . Field experience with threads made to this standard may indicate what limitations should be placed on driving speeds.—Interferences. chips.000 +. 3« • This table Is based on externally threaded members being ASTM A-325 (SAE grade 5) or better. 0.0088 . 10. DRIVING SPEED.417 4M -.. whereas with an unlubricated hole the minor diameter may tend to open up in some cases. -Depth of full lorm thread In bole. 850170' 51 .0084 . Field experience with a large variety of sizes and materials will be needed to establish adequate values. ASSEMBLY TORQUES FOR REAPPLICATION.0006 .250 2Mn -.-Length of engagement. 7. noo .—Gages in accordance with Part I. 4. 0. b L.+.. (c) Cleanliness. RELATION OF DRIVING TORQUE TO LENGTH OP ENGAGEMENT.0172 . TABLE 11.b T. since they contribute to interference and this is the purpose of the class 5 thread. +.0143 .—Holes shall be countersunk to a diameter greater than the major diameter in order to facilitate starting of the studs and to prevent raising a lip around the hole after the stud is driven. shall be used. Experience may dictate the need for imposing some limits under certain conditions. grit.000 1356*_...0055 . Field experience with a large variety of sizes and materials will be necessary to determine the torques which will insure the same performance where repeated usage is involved.-External thread length. 9.0015 .000 12 /8 IUb 'Mo 12 19 IMa I'M« IM 35 45 75 90 120 190 250 400 470 580 705 840 /(-» 3 6 10 15 20 30 37 60 90 125 155 210 250 325 M« 'Maj Moj ■Ma *H* H «M« 2 m* IMa Ma H m l'Ma l»i« M»j? »Ma •M» mu PMJ 'M«i 'Mo IMa 1« l'Ma +• mi IMoj *»-«1-8— 1W-7. cut.357 3M«: "-.b T» mln << Min £..0105 .0172 in. particularly in the hole.000 +.000 '-.0012 .0008 .0030 .0070 .227 '^-. .—This trial standard makes no recommendation for driving speed. the dimensions li ited herein will probably require adjustment based on pilot experimental work with the combination of materials involved. 8.278 2'Ma -. care must be taken so that an excess amount of lubricant will not cause the stud to be impeded by hydraulic pressure in a blind hole. In American research it has been observed that the minor diameter of lubricated tapped holes in nonferrous materials may tend to close in. "Not go" thread plug gages should not enter more than 1% threads. +. 6.179 11 "«-. Angle and lead deviations are not normally objectionable. «-10- in.0025 .0080 . H »5ia Wo 2 H »Ma in. oil. The lubricant shall be applied to the hole and it may also be applied to the stud.0020 . and torques.156 IMa . A noncarbonizing type of lubricant. • T.—This trial standard does not provide control for lead and angle deviations. (such as a rubber-in-water dispersion) is suggested.0003 . torque at 'ull engagement of l^D in ferrous material Engagement lengths. "-. 1 m 2M« 2Mo 2'Ma 2H 3Ma 3'/io 32Ma 4M m±: I'M«! 2H»t' w m 3M« +. Where such materials are used.. section VI. BREAK LOOSE TORQUES AFTER REAPPLICATION.000 +.0005 . 5..000 . Holes shall be clean from grit. It is (or rolled. a good lubricant sealer should be used.000 u.—This trial standard does not establish assembly torques for reapplication.125 'M"-.0143 . lubrication may not be needed.— This trial standard does not establish recommended reapplication breakloose torques in cases where repeated usage is involved.0025 .0116 .. class 5* Approx. «6 a H +. a lubricant should be selected which is insoluble in the medium being sealed.—Holes shall be free from chips. 357 m l Ma 1H J m 2». external thread lengths and tapped hole depths Interferences on pitch diameter Sites and threads per Inch In brass and ferrous In nonierrous except brass Max Max Mln £. "Go" plain plug and "go" thread plug gages should be inserted to full depth in order to detect the effect of excessive drill or tap wear at the bottom of the hole. silicon bronze. m w» m I'M.. M«-18 H-16hrU H-13M«-12 M-ll.3.0014 .000 3»Ma -.—(a) For driving in ferrous material.417 IH-01M-6. or ground threads. Recent British research recommends the use of medium gear oil for driving in aluminum. LUBRICATION.000 +. 1M-7.0030 IB.0092 . +. HOLES. • r.000 -.—(a) Inspection.0010 . lengths of engagement. or other extraneous material prior to gaging. [O) YYnen ciass o tnreaaea products are anven in nonferrous materials. n the fine series class 6 external thread may be followed in deriving the pitch and minor diameters of the internal thread for the fine series. Similarly.4. 2. adequate data is not now (1958) available to permit setting a standard on larger sizes.—Although there is some current usage of interference fits on large size threads.). Torque measurement methods. (6) For driving into brass and into ferrous materials having hardness under 160 Bhn. LARGE SIZES (OVER \\{ IN. sufficient tension must be produced in pipe flange bolts to exceed the longitudinal forces caused by the pressure in the piping.3 gives interferences and engagement lengths. and larger sizes in ferrous materials. The bolt is then tightened until it has elongated the required amount. (c) For driving into ferrous material of 160 Bhn and harder. however.—By using the new principles upon which this standard is based. SMALL SIZES (UNDER }i IN. elastic properties of the seating material. c) minimum interference. American research indicates that on smaller sizes the main reliance for producing adequate breakloose torques should be placed on pitch diameter interference and not on increasing the length of engagement.500. applicable only when the desired tensile stress is just beyond the yield point of the bolt material. as follows: 1. in ferrous materials. Since the modulus of elasticity is practically constant at 29. adequate data are not now (1958) available to permit setting a standard. (see g. or stud when the joint is assembled requires a method that either directly or indirectly measures or determines the amount of tension. (a) One set of pitch diameter limits is maintained for each size regardless of material. it elongates as the tension in the bolt is increased. screw. in which both ends of the bolt must be accessible to measure the change in the overall length of the bolt. or creep of the bolt under load.3 and in compliance with the above design and application data. The same problem is faced in tightening the nuts on the cylinder head of an engine block. 3. Micrometer method. the minimum major diameter is approximately that of the minimum major diameter for class 2A. 5. For lengths of engagement of V/J).000 $ effective length. Table 11. so that the studs are all stressed equally and to a tension that precludes leakage. so that the flanged connection does not leak. TORQUES. the length of the bolt is measured by a micrometer before tightening. 5. Indications are. a tolerance of plus 2% pitches. 3. The minimum pitch diameter is larger than the basic pitch diameter of comparable UNC series threads. the external thread length and depth of full form threads in tapped holes are set at \YiD with a tolerance of plus 2)$p.000 psi for all steels at room temperature. No research data are available now (1958) to enable the setting of a trial standard for fine thread studs having reduced major diameters. AK (WV) E1On ^tion = 29ÄööX5=00076in- To apply this method. which require that the torque-tension relationship be established for the specific conditions of assembly. "Feel" method. (6) The hole minor diameter limits are the same as those of class 3 for all sizes in nonferrous materials and for sizes up to and including % in.1 contains the limits of size for external threads. AND INTERFERENCES Tables 11. the length of engagement is 1% D. L. the length of engagement is V/t D. S6) stud pitch diameter tolerance. of 5 in.). Use of special devices for controlling tension. that the product of the ratio: Class 2A UNF PD tolerance Class 2A UNC PD tolerance and the following coarse thread characteristics will probably work: (a) stud major diameter tolerance. For %t in.1 and 11. In both cases. In statically loaded structures in which there is a clearance between the bolt and the members held together the clamping tension is important where rigidity of joints is desired to prevent relative motion of such members. and tapping hole depths specified in table 11. the range of the dynamic stress in the members varies with the bolt tension. however. and in some applications the amount of prestressing within a narrow range of tension is critical. The 8-thread series is now (1958) being investigated.2 contains the limits of size for internal threads. Extension of the standard is being investigated further. TABLES OF DIMENSIONS. the maximum and minimum major diameter limits are reduced to permit plastic flow and to reduce and stabilize driving torque. In the practical application of fasteners there are five generally used methods for setting bolt tension. Factors affecting the maintenence of bolt tension are the proportion of seating area to thread cross-section. However. 4. 8-THREAD SERIES. 1. For example. 2. external thread lengths. the length of external thread and depth of full form thread in the tapped hole are set at 2%D witl. Table 11. and a desired stress of 45. stretch of the bolt. minus 0. it contains one set of pitch diameter limits regardless of material involved.) Example: For a length L. To assure that such tension is actually induced in the bolt. THE TIGHTENING OF THREADED FASTENERS TO PROPER TENSION The effectiveness of a threaded fastener usually depends on the degree to which it is initially tightened.500. In the design of bolted connections.000 psi. and consequently the fatigue strergth varies with the bolt tension. Table 11. For driving into other nonferrous materials. The use of washers or other springy members in a fastener assembly tends to reduce the amount of external load that can be applied to a prestressed fastener before the load becomes additive to the initial bolt tension. 4. 12. In the laboratory the tension induced in a bolt by tightening the nut can be accurately determined in a tensile testing machine. the above prin -<oles observed in setting the pitch and major diameter limits v. the following formula applies: Desired stress in bolt in psi =elongation in inches per inch 29.—Use of the coarse thread series is urged unless requirements for strength of the stud make a finer pitch necessary. Angular turn-of-the-nut method. (a) For each size. EXTENSION OF THE STANDARD 1. MICROMETER METHOD When a bolt is tightened. the length of engagement is 2% D. and tolerances have been adjusted. 52 . In structures subjected to varying or alternating stresses. enough experience is generally available to determine the amount of the required tension. the minor diameters have been enlarged slightly in order to reduce driving torques.2 of the standard are based on engagement lengths. stud sizes may be extended downward.1. minus 0. For lengths of engagement of 2)$D. APPENDIX 12. FINE THREAD SERIES. Stewart. Carr. The le lgth of the pin is such that when the full load has been apriied. E. W. 62 (1947). 4. 0. if deemed necessary. Poncelet. ANGULAR TURN OF NUT METHOD A procedure that is consistently being used in the installation of high strength bolts in structures is based on the turn-of-the-nut method. Fasteners. 2. for many applications the tension may be controlled within satisfactory limits by applying known torques in tightening the nuts on the bolts or studs. As the bolt is loaded. 2. (Voss. (c) Tru-load bolt. FIGURE 12.2. Effect of initial tension in flange bolts. BIBLIOGRAPHY [1] J. For some applicati' ns. B. V. 945 (1931).» full preload. . TORQUE MEASUREMENT METHOD In most applications of threaded fasteners. and he stops tightening when he feels this yield.—This device consists of two concentric steel rings sandwiched between two closetolerance. Fortunately. it may be desirable to have the indicating pin exteni above the top of the bolt before tightening. Predicting bolt tension. (6) Load sensitive screw. N. Thus. Feb. Almen. This method is not practical for general use but may be used for spot checking. 5. threads per inch. The inner ring is smaller in diameter and higher than the outer by a predetermined amount. [5] J. A known preload in the bolt is indicated when the inner ring is compressed to the point where the outer ring can no longer be moved freely by means of a pin inserted into one of the peripheral holes. When tl e load is applied.. Draw up flange bolts more uniformly. This nut is then tightened through a specified fraction of a turn to produce the required bolt tension.—The "tru-load" bolt provides a positive means for indicating the actual tensile loading on a bolt by the amount of elongation. 16 (1944). G. 8 (1940). [6] J. 62. The change in resistance of the strain gage is read on a calibrated potentiometer as actual bolt tension. and tru-load bolts. INCHES K» -( 5.—Drilling for elongation detei mination when one end is not accessible.2. the pin will be drawn in until it is flush with the top < f the bolt. This change in distance is converted directly into unit stress by gaging with a calibrated dial gage. 7. Power.—Effective length applicable in elongation formula.. Nusbaum. (a) Preload indicating washer. Because of the fact that most of the applied torque is absorbed in indeterminate friction. AS ME. By applying a micrometer depth gage to determine the change in depth of the hole during tightening of the fastener the tension can be determined. hardened steel washers. Seaquist. H. 53 . 3. (2] F. 60. Tests in numerous laboratories have shown that satisfactory torque-tension relationships may be established for a given set of conditions. a change in the surface roughness of the bearing surfaces or of the threads. 160. Trans. but that the change of any one variable may alter the relationship markedly. It is then loosened sufficiently.) [3] Melvin D. Res. length. The nut is first tightened to seat the contacting surfaces firmly. Maney. "FEEL" METHOD Authorities agree that when an assembly has been properly designed. When both ends of a fastener are not accessible for measurement. Fasteners. 1. [8] L. 2. 14 (1944). Mach. 3. [7] W. the pin withdraws into the bolt. load sensitive screws. or a change in lubrication will drastically affect the friction and thus the torque-tension relationship. The micrometer method is applicable for bolts that are threaded their entire length or for bolts that are so designed that the elongation will be uniform throughout the length. The torque-tension relationship for a given set of conditions may be established by means of a torque-wrench in combination with a tensile testing machine or by the micrometer method described above. 2. w///////////////mt\ v/////////////mm FIGURE 12. 265 (1883).4. material. CrelleS Jour. if the diameter of the bolt or stud is sufficiently large an axial hole may be drilled in it.. Goodier. When a skilled workman is tightening a nut. 7 (1946). What torque? Fasteners. 1. Frottement des vis et des ecroux.—A screw is made load sensitive by having a special resistance-type strain gage potted axially at its center. S. it must be recognized that a given torque will not always produce a definite stress in the bolt but will probably induce a stress that lies in a stress >ange that is satisfactory. USE OF SPECIAL DEVICES FOR CONTROLLING TENSION There are some specialized proprietary devices available whose function is accurately to control the tension induced in the bolt.EQUAL I EQUAL —■ «|—EQUAL •4 EQUAL L. C. he can "feel" a very slight yield in the bolt when the yield point has been reached. 293 (1827). and E. They are known as preload indicating washers. the yield point of the bolt may be slightly exceeded without harmful results.1. [9] G. and will also vary with the elastic properties of the abutting material. A. Engineering aspects of bolt variables. Grashof. Casler. it is not practicable to measure directly the tension produced in each fastener during assembly. O. 16 (1946). [10] V. The relation of torque to tension for threadlocking devices. The pin usually is made to be flush with the bolt head surface before loading. RP 386. Theoretische Machinenlehre. It may also be applicable in establishing torque-tension relationships when a tensile testing machine is not available. Hillman. Whittemore. How tight should a bolt be? Fasteners. The distribution of load on the threads of screws. 1946. 1. A-10 (1940). 4. It consists of almost any kind of bolt modified to contain a pin inserted along the axis of the bolt. 6. 3. Iron Age.1. [4] H. These devices are operative even when both ends of the fastener are not available for measurement. L. The pin is in contact with the bolt only at the inner end. The angle through which the nut should be turned will be different for each bolt size. Jour. to just release the bolt tension. see figure 12. Am. Leipzig. the elongation produced in the bolt causes the pin surface to move below the reference surface. A dial depth gage reading of zero then indicate. 369 (1924). on which the pitch diameter tolerance is greater and a larger measuring load may be required to make satisfactory measurements.0368« . H. 1. using approximately twice the load to be used in making pitch diameter readings.+ 1-933357-w(l+cosec a') n (2) to(l + cosec a') (1) APPENDIX 13.130 (1947). W. C. whereas for threads having lead angles greater than 5° the necessary refinements in the calculations are presented. 0. 1.00000 16 14 12 10 9 8 7 6 5 4 3te 3 .750-in.65001 Minimum.11111 . Fasteners. « Equation (2). single-start Acme and Stub-Acme Ihreads 09°) Pitch. it is recommended that pitch diameter measurements on 8 tpi and finer be made at 1 lb. For coarser pitches and larger wires the deformation of wires and threads is less than for finer pitches.04061 . Lenzen. 0.14286 . 10 (1949). In order to measure the pitch diameter of a screw-thread gage to an accuracy of 0.43334 . hardened and accurately finished steel cylinder. 04643 .1. [16] Walter M. 07378 . it is necessary to know the wire diameters to 0.25000 . 16 (1947). p.40000 . recommended that for tpi coarser than 8.33333 . 13. 2 and 3. 05738 . formula (1) takes the form g=Ma. Brunot and W. The best-size wire. Accordingly.05164 .32501 ..04873 .38734 . 18.—Wire sites and constants. of the wires used should be as close as practicable to the size that will contact the flanks of the thread at the pitch line. To avoid a permanent deformation of the material of the wires and gagef it is necessary to limit the contact load.75000 1.03045 .06961 . 0. For a half-angle of 14°30'. AND BUTTRESS THREADS 2 The computed value for the pitch diameter of a screw thread gage obtained from readings over wires will depend upon the accuracy of the measuring instrument used. Part I.09745 .36545 .650013p 4 in.1032« .51645 Maximum. THREE-WIRE METHOD OF MEASUREMENT OF PITCH DIAMETER OF 29° ACME. Eng. [17] Richard H. 14 (1949). 0. 48751 . Accordingly.28571 . This would indicate that the diameter of the wires should be measured agiinst a hardened cylinder having a radius equal to the radi'is of curvature of the helical surface of the thread at the point of contact. [13] M.1. i • HiiM'd on zero leml ungle. Stub Acme. and Buttress threads.04304 . 0. It is.20000 .487263p 5 in. Fasteners.0001 inch by means of wires. TABLE 13. 1?. parts of which are applicable to this appendix. New bolt tension calibrator. the sides of the thread with a pressure of approximately ♦wice that of the measuring instrument. [121 K. and the value of the diameter of the wires used in the computations. Variations in diameter around the wire should be determined by rotating the wire between a measuring contact and an anvil having the form of a V-groove cut on a cylinder and having the same flank angles.08608 . A review of the use of structural fasteners for greatest economy.03228 . Prod. »=threads per inch=l/pitch. To limit the tendency of the wires to wedge in and deform the sides of an Acme thread. G. the coarser pitches are used on larger and heavier product. 54 . u>=\vire diameter. 0. The standard specification for wires and standard Practice in the measurement of wires stated in 1128 (1957) art I. to be applied only where the lead angle does not exceed approximately 5°. Wire sizes » Best. ACME AND STUB ACME THREADS (29°) The combination of small flank angle and large lead angle that is characteristic of Acme threads results in a relatively large lead-angle correction to be applied in wire measurements of pitch diameter of such threads. 2 and 3. Torque for bolt? and nuts.00001 in. Fasteners. As thus measured the limit on roundness deviation shall be 0.06250 . Belford.03480 . IM 2 m m .19491 . Studies of the bolting of a fabricated steam chest.00005 in. Hanneman. as the thread to be measured. [15] W. Fasteners.12911 . How tight is too tight? Fasteners. The simultaneous measurement of torque and tension in machine screws.05417 . 4 (1957). safety. 6.05414 . 14. 29° STUB ACME. Fasteners.08333 . Fasteners.17215 . Pickel.48726 Threads per Inch P== 1 n 1 2 in. Skidmore. 196. 1128 (1957) Part I. and it is recommended that the measurements of wire diameter be made between a flat contact and a 0.50000 .00286 . a= half-angle of thread. 0. F. The diameter. and for consistent results a standard practice as to contact load in making wire measurements of hardened screw thread gages is necessary. 12 (1955). [18] Richard B.06500 . 3. Tightening characteristics of nut and stud assemblies. Appendix 4. Furthermore. to minimize errors caused by deviations of the flank angle from nominal value. In the case of multiple-start threads the geometry is such that it is no longer feasible to make the usual simplifying assumptions as to the positions of contact of the wire in the thread. 5 (1959).04063 .[11] A.08121 . (a) SINGLE-START EXTERNAL THREADS The general formula 3 is: E=Mv+-i in which E= pitch diameter.86867 . [14] W.06456 .516450p 3 in. the pitch diameter be measured at 2% lb. 14°30'.25822 . P. with the abovestated exceptions as to angle of V-groove and limit on roundness.1. may be taken as U "=^r= sec a 0. therefore. * See Appendix 4. Milliken. Strength and clamping force of bolts.10000 . the contact load. 1. 6.24363 . 10. 13000 . in this appendix measurements of single-start threads (with lead angles generally less than 5°) are treated as they were in the 1950 Supplement to 1128 (1944). are applicable to wires for Acme.21667 .12500 . p. 7 (1958).10834 . 2. As with 60° ihreads it is not practical to U6e such a variety of sizes. o' = tan-1 (tan a cos X) X=lead angle at pitch diameter. 16250 .20658 . Stewart. to.07143 .32484 .13922 16242 .34430 . and dependability. A/„=measurement over wires. 12182 .14756 . it is necessary to use a measuring instrument which reads accurately to 0. 1857? . In the case of Acme threads the wire presses against.00002 in.16667 .26001 .07222 . 197.06091 .08125 . 5. Schmittner.516 450 n (3> for which values are tabulated in table 13. 430898 . 0.7917 . 184692 . 516791 .08608 .000005 .139 .E.03228 .324016 .25822 .324055 . For larger lead angles there are two procedures available that give almost identical results.065074 .000022 .3 shall be used. 16 14 12 12 10 8 6 6 5 5 6 4 4 4 4 3 3 3 2 2 2 2 2 in.644452 .rur BMMiuaru uiaiiieier-puuu uuiuuiuuuuiis oi j\uine or values oi Liiu term ^l-ruuseu a .129896 .000005 .000004 .000014 .10329 .7500 3.3760 1. 054335 .12911 .—Values for wire measurements of single-start standard Acme threads (39°) Change in cols.000005 .483339 .12911 .7000 4.645618 .52)725 . 2M \% 2H 3 3M 4 4M 5 Classes 5C and 6C centralizing M H y.322228 .) col.12911 .000007 . a check should always be made to ensure that the wires do not touch the thread root.966678 .17215 .291198 1.323395 in.05164 .25822 .000005 . E=M„-co\. However.161113 .516412 .386671 . 215795 .483339 .25822 0.12911 .000003 .2207 1.241670 .000022 .5833 2.000003 a H 1 H J* m 1W 1H 1H 2 m. 645346 . 3333 2.000010 .2500 4. and 4C centralising M M«-~ H H»—- in. 966678 .1220 1.215448 .5625 .000022 . TABLE for use when threads of other than standard diameter-pitch combinations are to be measured.290422 1. If the measured wire diameter.08608 .2188 . 644452 .430601 .258410 .483339 . 241670 . 108672 . 3) Sizes Threads per inch Basic pitch diameter Best wire sire.5418 2.290093 .17215 . (4) or.000014 .322226 .12911 .06456 .54187 .04304 .323013 .2032 3.19»33t> .2.000049 . 215937 .322226 .000011 .9985 1.10329 .0110004 .644452 .7067 3.860260 1.8396 2.1£311 .645221 . Hence. if E differs appreciably from the basic value given in column 3.081343 .7500 4.25822 .0458 2. 0.516450 Mi- cot 14°30' tc(l+coseca') Col. thus J?=M„.516846 . 081387 .323551 .12911 . 6 minus col. 2500 3.046595 . 516567 .161704 . the anal result should be rounded to four places. 55 .386671 .) from the best size.215916 . 7.645366 .000011 .000019 . w.25822 . Values for intermediate lead angles may be determined by interpolation.483339 .4500 .644452 . 8750 2.323532 .-col.08608 . (5) where Et=M„—col.290075 in. the correction derived from column 8 is seldom significant in amount for standard diameter-pitch combinations.324520 .860541 .290403 1.0003 in.000006 .6941 .000003 .324471 .000007 . 258370 .000008 .000019 .1500 1.25822 .386671 . 108:175 .065034 . After subtracting from Al".000006 .12911 . In those exceptional cases that have smaller lead angles the procedures described above may be applied.386671 .216118 . because of the shallower root on the Stub Acme threads.0833 2.138097 . 516443 .291149 1.120835 . 5 • All general purpose and classes 2C. differs slightly (not more than 0. 8.966678 in.516606 .10329 .000015 .645575 .1970 4. 4323 . (6) However.129935 .483339 .966678 . u 1 10 8 6 6 5 6 5 4 4 4 4 3 3 3 2 2 2 2 2 .) col.193336 .17215 .000022 .162236 .000036 .215300 . shown in column 4 E=M„-col. no smaller wire than the best-size wire given in table 13.430653 .162027 . 7-5 (w'-u>)-100 (col..860570 .000014 .108427 .01 in. 290210 1.000004 .05164 .000019 .t Stub Acme threads.25822 .860368 .323415 .322226 . 483.3. 3333 .5919 1. and if the best-size wire is used. w'. 966678 .0250 1. the computations are simplified by the use of tables 13.04304 . 3-E.3750 . 0.430964 . There can be instances when the best-size wire will touch the thread root. 17215 .1032» .860389 .2938 2.216808 .000030 . 644452 .161863 .130120 .7500 in.000008 . 162435 . 0. 8.6451 .323057 .000022 .860247 1.161113 .966678 .25822 .7683 . 216089 .2 or 13. 644452 .386671 .966678 .323744 .162279 .290733 1.161882 .000032 .6667 .000014 .000003 m IM IH I» 1»< 2 2M 2M 2)4 3 3M 4 4M 5 • Given to six decimal places for purposes of computation.3958 . 7-100 (col. 6 and 7 per 0. (b) MULTIPLE-START EXTERNAL THREADS Multiple-start threads commonly have lead angles greater than 5°.03689 . 129772 . 129741 .9000 1.483338 .10329 .25822 .10329 . 130175 . that is the discrepency between the values obtained for the 13.966678 .966678 .3444 1.06456 .000014 .290229 1.25822 .000030 . 3-. 3C.386671 .108738 . 0. The three-wire measurement of Stub Acme threads corresponds to that of 29° Acme threads.5427 .000022 . 290694 1. 162405 .000004 . 966678 .040869 . 483339 . 645774 .2500 1.0.08608 . 7.645202 .6250 1. 0..17215 . are given in iiauie lo.2768 . 17215 .162007 .000010 . change in pitch diameter (col. 645744 . 4700 .966678 .04304 . 0.108316 .12911 . 6 and 7 per 0.054294 .860533 .430800 . 0. change in pitch diameter (col.1900 1.184647 .000044 .064993 .860332 .1 the actual points of contact of the wire with the thread flanks are at A and B.000007 . 215477 258329 .4000 2.483339 . 6 minus col.081291 108574 .645669 . as this size is dependent on the lead angle of the thread.054364 . axial pitch screw and dividing by the threads per inch [15].10329 .17215 . Thus. equal in diameter to the wire.10329 .1 (9) (8) (7) TABLE 13.9400 1.966678 . is well within the possible observational error in making the measurement of pitch diameter.215880 . 193336 .644452 . 0. 3.08608 .993 929UI-1.9260 2.323942 .322226 .645310 . 161971 .966678 in.3000 1. 0.161422 .51635« .129949 .1500 2.138097 .4— Values of (1+cosec a') for a=H°S0' and lead angles from 0 to 6" 1+cosec o' Difference I*ad angle. X 1 deq min 2 30 35 40 45 60 55 3 0 5 10 15 20 25 30 35 40 45 50 55 4 0 5 10 15 20 25 30 35 40 45 SO 95 Lead angle.05164 .000003 .644452 .933 357/n c=2(OP-00) of figure 13. as follows: E=M„-(C+c) where E=pitch diameter Af„=measurement over wires C=«)(l + cosec a) . 216081 .322226 . lead angle correction.5 and references [15] and [21].000005 .4125 .000018 .483339 .000030 .000004 .323498 . 162179 .00003' .29822 0.215407 .TABLE 13.0650 1. M Me - H iu a 1 16 14 12 12 10 8 6 6 5 5 9 4 4 4 4 3 3 3 2 2 2 2 2 in.12911 .3.000021 .000021 .000005 .—Values for wire measurements of single-start standard Stub Acme threads (29") Change in cols.10329 .386671 . 046550 . 161839 . It is necessary to determine the best-wire size for the individual thread. 5 » 1 2 3 in.04304 .99393 393 394 396 399 403 407 412 418 429 432 440 449 499 470 481 493 506 620 539 550 968 983 601 620 639 659 880 702 725 0 1 2 3 4 4 5 6 7 7 8 9 10 11 11 12 13 14 15 IS 18 17 18 19 19 20 21 22 23 23 4.323678 . The conditions determining single or double contact are dealt with below.290620 1.000014 .162330 .25822 .8500 4 5 6 in.290049 7 in.3500 . 5 0 5 10 * See references listed in the bibliography at the end of this appendix.241670 .966678 . c.06466 .322961 .03228 .130036 .000025 .000012 .645518 .483339 .161113 . 644452 . After subtracting from M„ the final result should he rounded to four places.324357 .430542 .386671 .000014 . In figure 13.7000 .5875 .08608 .4260 1.4 based on the analytical approach of Gary [22] and of Vogel [21]. 516620 . w=wt/n The pitch diameter is given by formulas.03689 . in which case it is advisable to use a ball.17215 .2312 .000004 . 8 Sizes Threads per inch Basic pitch diameter Best wire sine.12911 . 161113 .129685 . 0.25822 . 215766 .040587 .916450 n cot Utff 2n t»(l+coscca') Col.8600 4.2911 . X 1 deg min 0 0 6 10 15 20 25 30 35 40 45 60 96 1 ft 9 10 15 20 29 30 35 40 45 50 99 2 0 9 10 19 20 25 1+cosec o' Difference 2 3 2 3 4. axial pitch screw are also given in table 13.(cot o)/2n = 4.645178 .000007 . 0.000003 H H % m IM 1M m m m - -- 2 2M 2H 3 3M 4 m 6 • Given to sii decimal places (or purposes of computation. 483339 .12911 .290176 1.6600 2.8600 3.01 in.000004 .386671 .25822 . 56 .8250 .3600 4.00026 058 091 125 160 195 231 268 306 345 384 424 465 907 950 593 637 682 728 775 823 871 920 24 29 26 27 27 28 29 30 31 31 32 33 34 35 35 36 37 38 39 39 40 41 42 43 43 44 45 46 47 48 48 49 (10) Tabular values for (C+c)i for a 1-in.290356 1.99748 772 797 823 860 877 905 934 964 995 5.000019 .000011 . The methods are those of Marriner and Wood [26]. Under certain conditions a wire may contact one flank at two points. which should be divided by the threads per inch for a given case.3600 3.860218 1.000014 .323371 in.000021 . The value of c is the same for a ball as for a wire.6750 1.966678 .17215 .5 the wire diameter (interpolating if necessary) for a 1-in.291035 1. This determination is simplified by extracting from table 13.120835 .25822 . 516707 . 64218 .62906 .63715 .50488 .63537 . in the axial plane containing LA.64311 .62956 .62672 .50815 .62699 .50632 .49959 .64272 .50561 .60864 .7 8.50658 .50464 .51238 .64072 .6 7.51243 .51069 . 62598 .2 5.49914 .63649 .51285 .1 12.62312 .50768 .(^7C°ta).62520 . 0.63802 .51384 .50606 .64291 .62253 .63206 .62509 .0 7.51368 .50175 .62546 .9 13.50965 .63793 .50847 .63195 .9 10.4 8.9 6.5 10.63704 .64021 .7 14.1 11.63271 .62981 .8 14.5 8. axial pilch Acme and Stub Acme threads (29°) 1-start threads 2-start threads «01 2-start threads Lead angle.51435 .63630 . respectively.51320 .5 6.63436 .50849 .63050 .50352 .2 12.6 6.2 14. 5 in.62368 .7 6.2 8.63250 .50955 .62537 .8 13.3 6.64085 .50073 .63555 .50432 .64245 .51366 .62442 .51393 .63817 .63831 .51186 .51142 .50571 .64097 .6 14.63027 .50131 .62645 .5.4 12.49891 57 .63102 .63612 .9 15.63744 .62564 .63693 .51221 .62718 .6 5.51450 .50800 .50003 .51336 .5 14.64171 .51162 . Letting 0=0.50482 .51227 .51232 .63420 .64110 .63972 .5 7.62865 .64089 .51125 .51403 .8 9.To evaluate c 2(5-sin ß+y sin a cos ß f OP=y cos a cos ß+ (ID vWfj OQ=R+»cosec a (12) 7=distance from contact point .4 6.62817 .4 to a point L on the thread axis.62391 .9 7.50173 . 50295 .64134 .l 5.63219 . X toi 1 deg 5.« 8. 51377 .50500 .51138 .62417 .1 6. TABLE The values of ß and 7 are determined by the following equations: w / I cos ß .64251 .63909 .51327 .62888 .50951 .50135 .64282 .63987 .51198 .50413 . j \t iß 2x sin a (14) These are simultaneous equations in ß and 7 which cannot be solved directly but can be solved by iteration.62621 .62958 .51093 .64034 .63843 .63873 .49988 .51088 .64256 .50927 .63395 .5 12.50030 .63498 .63518 (C+C)i 5 in.63117 .64002 .64196 .63876 .63722 .64122 .50517 .51386 .63311 .1 14.4 13.59115 .3 14.50993 .63457 .1 10.63810 .50751 .61442 .64047 .50993 .50214 .51035 .50968 .0 12.63399 .50051 .50981 .62792 . 61395 .62646 .64279 .82768 .50691 .51443 .64144 .63892 .51032 .50535 .51044 .51022 .50235 .7 7.7 12.63944 .50215 .49936 .51275 . A ~ I tan a sin ß 1 .7 13. /S= (designated the "key angle" by Vogel) angle in a plane perpendicular to the thread axis between lines connecting the point 0 on the thread axis.6 9.62841 . .6 8.50275 .63126 .62619 .63333 .64061 .50864 1 deg 10.63292 .50445 .2 11.64240 .51259 .50674 .63845 .63313 .50771 .3 13.64160 .50755 .50068 .62468 .51411 .61186 .63957 .60913 (C+c).63172 .61419 .51340 .62934 .50589 .0 6.50879 .51150 .50908 .51153 .8 12.50707 . 62397 .4 14.63574 . „ 2 \2TT7 cos a / (13) sin 0= -— Mi)' 7=-— + COS a R .63031 . 0.64221 .8 6.64195 .50507 .64075 .51346 .50333 .0 4 in. measured parallel to an element of the thread flank.63356 .50356 .63859 .50255 .50394 .60941 .51101 .63775 .50979 .4 7.63006 .2 6.51401 . 0.63228 .50802 .50544 .62779 .50615 .6 12. 51019 .63667 .9 11. the first approximation for 7 is ?o = ß sec o+-s cot a (15) 13.3 6.62881 .51062 .51164 .63162 .61280 .51174 .50375 .0 14. 51057 .63288 .50110 .62830 .51217 .50024 .63078 .C+c).51075 .64301 .62694 .62481 .5C/84 .51113 .50254 .51427 .51008 .64117 .62340 .—Best wire diameters and constants for large lead angles.7 11.50293 .63149 .50389 .62981 .63758 .62494 .51356 .64233 .51118 .3 8.2 9.50313 .5 9.62365 (C+c).0 9.51264 .64229 . 62725 .63140 .50046 .62911 .7 6.51359 .63375 .6 6.50553 .50649 .50641 .6 13.63930 .64290 .3 11.51317 .63941 .63774 .50408 .61249 .64207 . 51435 .50194 .64172 .50526 .1 8.63996 .64261 .64046 .63859 .4 9.62283 .50667 .63827 .51081 .6 10.51410 .50195 .2 7.63265 .50427 .5 13.50718 .5073» .62805 .51206 .3 10.50336 .0 11.63970 .3 7.49981 .63242 .63095 .51006 .63463 .8 10.62425 .50786 . 0.62592 .9 9.63887 .50623 .50094 .51105 .64017 .50152 .60834 .64103 .51330 .63730 .0 13.51296 .63378 .51306 . 62743 .4 6.8 8.62856 .63788 . 7 in.63902 .51175 .63055 .49945 6 in. 51049 .51130 .63685 .0 10.6 11.7 10.2 13.51270 .50701 .50684 .64008 .64184 .50893 .2 10. X te>i 3-start threads id Lead angle.51300 .50723 . 62453 .63740 .50579 .64157 .50937 .50470 .50451 .49966 .63416 .5008» . 0.50274 .63916 .63518 .63333 .62670 .8 11.64209 .64060 .62195 4 in.63184 .1 9.50818 .50316 . 1-in.63478 .4 10.62224 .63759 .8 7. 0.8 11. to the axis of the wire (or center of the ball) and to the point of contact of the wire and thread flank.63072 .62571 . 51375 .50831 .63983 .51350 . 51310 .64032 . 3 in.51418 .51209 .4 11. 0.9 12.1 7.63354 .9 14.64147 .50009 .64131 .639U5 .64268 .0 S.62931 .0 8.1 13.51196 .62752 .50234 .51427 .50371 .63700 .63957 .63004 .50922 .64184 .3 9. 0.0 2 in.63442 .50735 .63685 63670 (.50155 .51290 .7 9.8 5.50597 .51254 .3 12. 62481 .49936 . 49864 .60241 .60549 in.12732 39545.49285 . 21]. 50255 .49635 .62202 . 7o= .50194 .60976 .01621 13939.61383 .49127 .50024 .0 16.61350 . cot « = 3.2 13.61389 . 0.59920 .025.62195 .60835 .62048 .61661 .49699 .48712 .49463 .49754 .47845 .4 17. This process is repeated until the values of ß and 7 repeat themselves to the required degree of accuracy.48854 .49627 .60817 .60002 .59293 .61458 . 0.7 18. R/cos a= . 47610 .60359 .49602 .62049 . Their final values are then entered in eq (11) and (12) to obtain the lead angle correction given by eq (10).59336 .48134 .62232 .1 14.62498 .60871 . .48596 .48943 . 48292 . 21].96814 76404.8 20.61770 .31830 98862.62619 .50316 .7 20.49180 in.50152 .61895 .32966 49520. 0.48915 .50003 . tan a= .50214 . sec a = 1.59715 .62368 .6 15.49400 . TABLE 13. </(2ircosa) = .48887 . 62340 .49659 .4 13.01250 .47943 .48800 .2 20.49512 .3 19.61921 .48008 .50043 . 2 (//2T) = .2 19.61801 .61283 in.7 15.60585 .62453 .49233 .60693 .50173 .99392 91629.48971 .4 20.61738 .—Best wire diameters and constants for large lead anales.49438 .48859 .0 17. 11 .6121.9 22. 1-in.4 15.61037 .5 15. 0.59590 .49611 .61250 .60123 .48445 .6 13.61760 .60437 .49020 .1 22. 50131 . Then this new value of ß is entered in the right-hand side of eq (14). 58 .49191 . 0. V>i" — 5.« 20.8 22.48476 .61628 .5.49154 .3 13.9 15.5 21. cosec a = 3.31916 43455.49891 .61073 . Z=0. 49910 .62469 . together with the first approximation of 7 to obtain a new value of 7=7.61987 . X 3-stnrt threads (C4f)i 4-start threads Lead anplo.59507 .0 19. sin a=0.62699 .61953 .49164 .62283 .48742 .8 19.2 16.2 21.60162 .59674 .1 17.1 13. cos a= .13151 29523.62110 .49651 .48103 .5 19.61926 .50152 .50046 .209.5 22.62108 .—This table courtesy of the Van Keuren Co.50295 .2 14.61793 .61144 deg 18. nominal.3 17.62291 .4 21.49537 .62080 . 62555 . 62537 . 62667 .62351 .47677 .49363 . 62526 .02752 .48713 .47975 .60666 .61857 .59379 .60742 .50110 .50275 .49451 .49488 .48230 .48910 .50852 28550.50235 .50089 . X (C+c).5 14.8 16.27393 42429.61956 .8 14.0 13.1 21.9 23.61833 .61492 .50173 .« . den 13.8 21.47577 in.2 22.48882 .49824 .60281 .4 14.61548 .62172 .81594 .60202 .61694 .47878 .48938 .62312 . 49707 .61643 .61580 .49375 .49074 .60628 .9 19. 62672 .48684 .48825 .48769 . 62725 .9 16. 62321 .61182 . X=13.2 15. l/x= .49109 . 0.3 22.0 14. 57.49322 .48620 .48625 .9 in.5.f 19.49914 . 60657 . 62592 .49562 .7 13.49137 in.47643 .6 21.61216 .48384 . p=0.48830 .50068 .61706 .61449 . 50297 .9 14. 48597 in.62583 .61675 . 62639 . 49842 .47778 . and the result may be compared with that obtained for the same example by the Vogel method [21] or the Van Keuren method utilizing tables [15.50256 .49801 .8 18.59207 59164 .49027 .7 22.48965 .60906 . axial pilch Acme and Stub Acme threads (29°)—Con.61424 .1 20.This approximate value of 7 is entered in the right-hand side of eq (13) to obtain a new value of ß—ft. 49527 . R= .49502 .60590 .800.60083 .49887 .49259 .47745 .48536 .62425 .49054 .3 15. 49795 .59250 .50109 .50087 .(»1854 .10020 (from table 13.48797 .« 22.49389 .61080 .3 21. l/2*= .48566 . 60621 .25038 00041.62166 .5 13.9 20. 18.49675 . 3-start threads (C+o). Then 71 and ft are entered in eq (13) to obtain a new ft=ft.47910 .4 22.6'.48683 .0 in. 4-start threads (C+Oi Lead anjrle.62509 .62397 ..3 14.62141 .62017 .50021 .60780 .59838 .60042 .49683 .61611 .25861 75844.59632 . 49959 .49955 .49846 .49771 .61889 .1 1* 2 lev 3 is.62137 .59465 .50215 .48198 .61825 .49311 .62253 .3 16.60552 .59548 .49999 .60764 .48071 .49206 . 49731 .50065 .5°.47711 .9 17.49723 .49082 .8 17.61354 .62381 .4 19.60514 .1 15.0 21.7 16.48415 .6 16.47812 .60941 .50277 .49414 . [15.59756 .49047 .49819 . 49981 .49217 .7 17.5 16. 4 start 29° Acme screw thread E= 1.50131 .61727 .49586 .50235 .0 22.62440 .62564 .59961 .60729 .61011 .49269 .9 21.61114 . 48ixiC» .60964 .48992 .7 19.49337 .1 19. 49747 .5 17.49243 .48741 . 48323 .48771 .49977 . 49577 .0 18.6 18.62646 .3 20. 49101 .48999 .61180 .61985 .60320 . 49552 . 0.48040 .48354 .61416 .61319 .49932 .59121 NOTE.61526 .6 14.61148 .0 20. «=14. 62694 .60475 .49296 .61316 .8 13. 62262 .61482 .61864 .60928 .48261 .5 20.6 17.62611 .62017 .61284 .2 17.60704 .0 15.60398 .59422 .5 18.60891 .60799 .03290 03122.951927° u»=0.62078 . The following calculation exemplifies the process.48166 . 49778 .61001 .61560 .7 14.86671 30949.7 21. p.48655 .61045 .50194 . 49476 .4 16. 0.59879 .61109 . Z/(2Tsina)= .8 15.1 16.62224 .61515 .49349 . 48655 .59797 . 49425 . double contact does not necessarily occur when these formulas are not satisfied.54444 . The measurement to the center of the wires is given by the Vogel formula 2 OP=E tan« X(<y-/3) cosec (3=1.02232 480 radian.52483 3962 00-0.02232 501 obtained with the Marriner and Wood formulas. 2. (20) When ai=45° and O3=70.000 018 in. and nontranscendent formula for ß.149 888 ta. Also. 54446 . For all possible singlestart combinations of diameters and pitches listed in tables XIV. but various short cuts are presented in reference [21]. w.15689u> .011 148-0. Then. 99975 . it is not essential that the absolute value of the pitch diameter be accurately determined by applying When the lead angle and diameter of a thread are such that double contact of the measuring wires occurs. is computed using the formula E=M„ P tan at tan «j (i i 1+cosec 0ti+O2 —s— cos ~ V* ' """"" 2 a (19) OP-0. V^(rl)' 0.933 357/5-0.0004 in. (see equations 8 and 9) C-4.52936 -. including a short.02232 . the discrepancy between the value of (C+c) by the Marriner and Wood formulas and that extracted from table 13. 99975 686 214 073 081 081 0807 0.99975 .=number of starts X=lead angle at pitch line a=half angle of thread in axial plane.2. In both formulas 20 and 21.—Basis of lead angle correction for external thread. 74 = final value for y in the correction calculation (0. using the average diameter of the wires. the condition for single contact simplifies to: in-plane with lead (with no lead.. XIV.89064p-3.c.54446 168 850 357 655 526 5336 sin<3 ß (radians) costf 7 On account of the approximate nature of the above formulas.0496 522 in.02226 .02226 . the pitch diameter.0000 157 smaller than the value (1.149 868—actual measurement over wires £-1.-nominal measurement over wires M. 02232 . In the optional method. 0-0) ■WIRE POSITION WITH LEAD jz-plane y-LA (with lead) t"LA' (with no lead) FIGURE tan (18) 13.(ßA—ßp) +(yA sin a sin ßA -^ cos fti^Xsec ßP sin (ßA-ßp)>0 in which.53865 . The comparator reading Mw over the wires is checked using a gage block or combination as a master. 52978 . it will be necessary to check the pitch diameter by means of balls rather than wires.99972 .52936 8598 would be the yA for sample calculation.02337 . which is 0. this formula reduces to E=il/„+0. c is a correction depending on the angle the wires make with a plane perpendicular to the axis of the thread plug gage.52936 . as compared with 0. If not satisfied the following formula can be used for a more precise determination: 325 621 984 853 860 8598 0.-1.149 868-0.113 720 C+c-0. tan a—iA sin «+Ö. The value of ß in the above example which satisfies this equation is 0.100 20-1. highly accurate. 13. 02232 088 331 647 298 317 3160 0. N.993 929X0. /3p=cos-' (2yA cos a cos ßA/D) and is a negative angle.99975 . This equation may likewise be solved for ß by iteration. c is less than 0.54486 . and XIV.89064p -1.02232 . D should be slightly smaller thai the major diameter of the thread plug gage to be measured.01114 8 2 OP-1.54446 .4. As this discrepancy is small compared with the possible error in measurement of Af„. BUTTRESS THREADS Two optional procedures are used in determining the pitch diameter of external threads from the reading over the wires.0496 679) obtained by the Marriner and Wood formulas. If the formula is satisfied.-2 OP-r-te-1.113 720+0. POSITION WITH NO LEAD (17) •me in which a=half angle of thread in an axial plane J=lead R—distance from thread axis to sharp root (see fig.02232 .1) u>=diameter of measuring wires D—major diameter of thread If best-size wires are used.124 868 E-1.52936 . the results of which are shown above.02232 301 515 833 483 502 5012 0. double contact does not occur. 52936 . 52934 . A/„. 99975 .02337 .3. E.15689 w-c.. the distance T between the wires as seated in the threads of the thread plug is computed by formula T=D-MD+MK and the formula for pitch diameter E becomes E = T+ tanai + tanof2 i «1— «2 •— w / I cosec «i — + <»!1 cos-"-----—1 ~\ \ 2 * 2 ')(21) I —c £= T+ 0.025 000 (as measured) If instead of the Marriner and Wood equations those of Vogel are applied we have cot*X -ß=tan a (16) cot ß— tan X where "-2N.124 868-1. either set of formulas is applicable.tan *>W1/(Ä+2£ cos a cot aY-4/Z>*. (e) LIMITATIONS ON THREE-WIRE MEASUREMENT OF EXTERNAL THREADS l—a2 2 )-. ßA —final value for ß in the correction calculation.149 868-(C+c). so that contact is near the pitch line. Then. 02232 . Measuring wires can be used if the following formula [26] is satisfied for a specific thread: 59 . As Buttress threads are designed to avoid metal-to-metal fits in all cases. a reading MD is taken over the wires placed on either side of a plain cylindrical plug gage of known diameter D.02232 .31926 0196 c-0. For accurate measurement with wires single contact on each flank must occur.1.04966 79—nominal measurement between centers of wires JW.5 is only 0. 0055 .6. it is recommended that the wire angle correction be neglected for these combinations and all other single-start buttress thread plug gages.40000 .890643p-u){H-V66.0112 . Jeffcott.43318 . The relation of the "best" and "max" size wires to the flanks and crests of the 7°. for symmetrical threads.0224 .890643 [V66. Such double contact will introduce on error into the measurement of pitch diameter. [8] G.0438 . December 1927.179« .04512 . Präzision. Tomlinson.330378(l+tanäX) + l . Proc. Correction for rake in screw thread measurement. 1. 06250 . für Iustrumentenkunde. [6] G. [9] Earle Buckingham. 59.Vtan'X + 2l} (23) For larger lead angles formulas may be applied that are derived in reference [22]. 114 (1923).+ l] } where ai=flank angle of pressure flank. (24) TABLE Threads per Inch Pitch.08333 . the "best size" wires.).330378( 1+tan^X) +1 . 0. pp. Proc. (1923). For this reason it was decided that the diameter of the "best size" wire should be such that it will contact the pressure flank at a point twice the distance above the pitch line that the contact point on the trailing flank is below the pitch line. Zeit.1122 . Inst.0541.—Wire sizes and constants. [3] Derivation of the general formula for pitch diameter measured by the three-wire method. diameter. [2] O. [4] E. Tomlinson.2.0898 . If this wire fails to project above the crest of the thread in an actual case.33333 . having a diameter of 0.1094 . 466 (1924). An alternative method for determining whether or not single contact occurs is to apply the Marriner and Wood [26] formula 19.SI433P •0. ^2) MAX WIM DM BEST WIRE 0/4 •O. 25001) . The National Physical Laboratory.0187 . for the exact condition for single contact.06143 . [10] G.02707 .the correction c. which contacts the trailing flank at the pitch line should be used. Mechanical Engineers.1496 .1944p below the thread crest. 30.2. Accordingly. single-start Buttress threads (7°. IC-0. a2=flank angle of trailing flank.54147P in. 0. Die Messung konischer Gewinde. 1IKKW) .0875 .2244 20 16 12 10 8 6 5 4 3 2H 2 o. 5. Appendix I.80000 1. it is desirable in such cases to check the pitch diameter measurement obtained with "best" wires by measurement with "max" wires also. 60 .15358 . 45° Buttress thread is shown in figure 13.0280 . No. If double contact occurs with max wires it will be necessary to make pitch diameter measurements by means of balls.2(10(10 .03384 . Machinery (London) «8.61433 o' -0. A. A. 45°) "liest" wire For the 7°.36098 .40955 . Die optische Messung des Flankendurchmessers von Gewinden. aj.54147 Projection. Double contact is less likely with the "max" wire than with the "best" wire.10829 . NBS Letter Circular LC23.0.61433p in. Limming.30716 .0140 . Machinery (London). 360 and 759 (1922). A. M. BIBLIOGRAPHY ON MEASUREMENT OF PITCH DIAMETER BY MEANS OF WIRES [1] H. P diameter. December 1907. Machinery (N. "Max" wire Projection. The diameters of "best" and "max" wires and the projection above the crest of the thread are shown in table 13. A deviation in the angle «i of the trailing flank has approximately twice the effect on the pitch diameter calculated from readings over wires than the same angle deviation on the pressure flank angle. 13. Vol. [5] E. Machinery (N. 0.+ l sin (oi+a2) —\/(l + tan2 X) cot* a. Berndt.18049 .13537 .Y.66867 . WIRE SIZES. Eppenstein. Limming. as the former contacts this flank nearer the thread crest.Y. 439 (Nov.00000 » i 3. Mechanical Engineers. X=lead angle at pitch line. With large lead angles a further check should be made using balls instead of wires. 22. 21.1094p III. and the wire will project above the crest 0. [7] G.49146 . + l sin (oi+a2) I -C0^lSi"°2 [V(l + tan'X)cot>«.03072 . Notes on screw threads. 1922.0274 .0561 . This wire diameter for flank angles 7°.147 . 25. Because of the small pressure flank angle of 7° there may be double contact of the wire on this flank if the lead angle is more than a few degrees. Normal thickness of a worm thread.61433p. Cylinders and spheres for gauging worm or screw threads.—In order to eliminate the effect of deviations of the thread form on the calculated pitch diameter. should contact the flanks of the thread at the pitch line.1(5667 .0364 . 1067-1108. 45° Buttress thread this formula becomes ß=M„+0. awon .07679 .12500 in. 1 (1938). Therefore.50000 .10239 .06768 .0747 . Berndt.0. (1909).03840 . 45° is given by u>t=0. Correction for elastic compression in the measurement of screws with small cylinders.20478 .12287 .0449 . if it is desired to take the lead-angle correction into account. p. 1031-1036.05119 .1 . 0. o-0.1094p.09024 . the "best" size wire will contact the pressure flank of a thread of basic form 0. Neuss (1937).S4I47P FIGURE 13.0091 . 1939).6. Die Bestimmung des Flankendurchmessers von Gewinden mit symmetrischem Profil nach der Deridrahtmethode. For such a case the maximum wire.0137 .). 616 (1926).54147p. However.0374 . As shown in figure 13.21659 27074 . 45.0219 . A.0068 . io»0.0182 .0109 . Inconsistencies in results may indicate double contact of wires. the following formula to determine pitch diameter derived in reference [3] may be applied where the lead angle does not exceed 5°: E=M„+VCOS«lC°8°2-w | l+V(l + tan»X)cot>«.H. Reprinted in Collected Researches.—Diameters of "best" and "maximum" thread wires for avttress threads.2244p in.2. a larger wire must be used.24573 . Because of the wide difference in the flank angles of a buttress thread it is impossible for the thread measuring wires to contact both flanks simultaneously at the pitch line. Inst. Pin method of measuring worms and helical gears.0729 . " However. (1948). in which the recommended ISA series are listed. ISA Bulletin 26 and the national standards set up in accordance with it. Berndt.) [15] H. [13] D. Switzerland. 1940). Efforts toward international unification of these systems led in 1898 to a conference in Zurich. 177. inclusive. and standard series for metric and inch screw threads. Effect of differences between U. 412 (1956). The Van Keuren Co. Braunschweig. L. On precision screw threads. Wolf. Prüfen und Messen von Gewinden. 18.). Determination of the thickness of the teeth of worms and spiral-toothed wheels with the help of rollers and balls. [22] M. Appendix D. was not published until September. *». 206. organized in Europe during and after the first World War. the pitch being 6 mm for all sizes above 80 mm. 36. Mass. Germany. 1. 1950. J. Van Keuren. The threads were intended for use as fastening threads in machine construct ion and hence for application to the general types of screws. [21] Werner F. London. 34. explicitly refer to the ISA Series B to E. Nickols. were also invited but did not send delegates. It took several more years to put the final touches on this unification plan. (Unpublished. für Instrumentenkunde. which de9ne the limits r' t. led a numl>er of Continental European countries to extend the original SI series. Screw Threads. Formulae and corrections for use in the measurement of the effective diameter of parallel screw ?lug gauges by means of small cylinders. Tables for precise measurement of screws.M127J) 61 . (Unidentified Russian publication. and ISO/TCI. 14.und Innengewinden nach der Dreidrahtmethode oder mittels zweier Kugeln. 21. Williamson. [12] G. Die Berechnung der Gewinde-Anlagekorrekturen. these additional series showed differences in respect to nominal diameters. Machinist. (April 1951). and nuts. C. 2. Following the war the International Organization for Standardization (ISO) was established. particularly in France. "Sy-teme Internationale"). was designated as "ISA Series A. Munich (1952). [25] L. Therefore. designated by the letters A to E.i the allowances and tolerances. [17] M. The best wire for over wire measurement of general screws. [26] R. 10. Varnum and S. 47. [18] Gauging and Measuring Screw Threads. 14. und Präz. Watertown." The ISA became inactive in 1942 as a result of the second world war. M.S. [23] M. Vogel. agement pour l'lndustrie Nationale in lav-t. Feinmech.).) M. Report of the Institute of Industrial Science. G. with its upward and downward extensions. as "fine threads. [16] F.. Translation available at NBS and Van Keuren Co. mis »vsic-m became known as the "International System" and is usually designated as the "SI S'stem" (from the French name.86603 p j -0. Effect of elastic modulus on measurement of thread wires.1.[11] N. J. and British practices in measuring screw gages for Unified threads. of Tokyo. bolts. 1940. 1. [14] Werner F. The need for metric coarse threads in sizes smaller than 6 mm and larger than 80 mm. Günther and H. Gary.—ISO basic profile for inch and metric screw threads. The original series of SI coarse threads was extended to diameters as large as 600 mm (about 24 in. 602 (1952). Physikalisch-Technischen Bundesanstalt. (1955).. National standardizing bodies. New thread measuring formulas. Ogawa.ic external and Intcrnal threads. this committee succeeded in getting agreement in principle on five recommended series of metric threads. Production Engineering and Management. Gary. Section VII. and diameter-pitch combinations. No. 1. and of metric fine threads. made an effort to bring some order in these additional series. which was attended by representatives from engineering societies and other technical organizations in France. Catalog and Handbook No. [24] E. the term "coarse" threads was avoided and the original SI series. arc app'ied. (July 1958). S. However. and ISA Bulletin 26. METRIC SCREW THREAD STANDARDS Metric-thread systems have been used in European Continental countries since 1848. The Van Keuren Co. Die Messung der Flankendurchmesser mehrgängiger Gewinde mit drei Drähten. Machinery (Lond. held its first meeting at Paris in 1949. 129 (1939). [20] W. No. 723 (1957). Geometrische Probleme bei der Vermessung von zylindrischen Evolventen-Schnecken und Evolventen-Schrägstirnrädern. Wood. R»ke correction in the measurement of parallel external and internal screw threads. E. Zöllner. Organizations in other countries such as the United States and Great Britain. The Basic Profile L* the profile to whlc'. Harrison. Johnson. BarberColman Co. The Zurich Conference of 1898 adopted a system of metric threads which was practically the same as that previously developed in France by the Sociötc' d'Encour- PITCH tEFHCVVC} OlAtXTC* FIOTRE 14. Analysis of screw thread measurement. The Van Keuren Co. Inst. H. L. Catalog and Handbook No. Marriner and Mrs. Konstruktion 8. with associated (coarse) pitches. 1951. No. Italy. (Aug. Germany. Litvin. Die Anlagekorrekturen bei der Bestimmung des Flankendurchmessers von symmetrischen und unsymmetrischen Aussen. W. and Switzerland. [19] F. At a conference held in Copenhagen in 1931. inclusive. the Netherlands. July 6.1. (1940). 4 (1955).21651p A -'-010829p -1I-0. of Mechanical Engineers. 34. Werkstattstechnik und Wtrksleiter. Zeit. This technical committee subsequently developed recommendations for basic and design thread profiles. This system was recommended for adoption by all countries where metric threads were used ana covered a range of nominal diameters from 6 to 80 mm. ISO THREAD PROFILES The ISO basic profile for screw threuds is shown on fig. 277 (1940). and Switzerland. 272. National hysical Laboratory. Precise formulas for overpin measurements of helical forms. Vogel. 237. 141. 11-0. The ISO design profiles of external and internal APPENDIX 14. pitches. Univ. (1957). In 1926 the International Standards Association (ISA) was founded and one of its first technical committees dealt with metric threads. —ISO design profile of external and internal threads without an allowance for inch and metric screw threads. AXIS OF SCREW THREAD FIGURE 14.1 covers metric screw threads for general use. the letter is S. These ISO basic and design profiles apply to inch as well as metric threads. (ISO Basic Profile shown by a thick line. the coarse pitch is implied. (ISO Basic Profile shown by a thick llnf \ 62 . the letter is M. vviKU ctiiu IYIMIUUU nil aiiuiviiitut*.) -IN PRACTICE THE ROOT IS ROUNDED AND CLEARED ABOVE DIAMETER D INTERNAL THREAD (NUT) D(On) d(Ds) «or») 4.1K1<_ ltlK&AUS figures 14. Table 14. arc BIIUWI1 Uli Ö. bolts. ISO metric threads are designated by a letter followed by the size and the pitch as shown below. «V PRACTICE THE ROOT IS ROUNDED AND CLEARED ABOVE OIAMETER D •D«V NUT DIAMETERS BOLT OR SCREW DIAMETERS IN PRACTICE THE ROOT IS ROUNDED AND CLEARED BELOW DIAMETER 4 AXIJ OF SCREW THREAD FIGURE 14.1 and 14.2.2 are the standard series for ISO metric threads.2 covers metric screw threads for screws. UE.) BOLT OR SCREW DIAMETERS IN PRACTICE THE ROOT IS ROUNDED AND CLEARED BELOW DIAMETER 4. STANDARD SERIES FOR ISO METRIC THREADS Shown in tables 14.—ISO design profile of external and internal threads with an allowance for inch and metric screw threads. and nuts. 2. coarse pitch).2 and 14. Where there is no indication of pitch.(K. For all other threads shown in the tables. Examples: M6X 1 (indicates 6-mm diameter. 1-mm pitch) S0.31U1NH11U1MC rUK 1ÖU IV1£.3.luu&auo.8 diameter.3.8 (indicates 0. Table 14. For coarse threads with diameters up to and including 5 mm. 75 .5 1.5 1.95 2.2 mm mm 0.276 .5 .5 2.433 .236 .5 1.7 .0276 .669 .5 1.5 1.5 1.76 2.30 1.75 .630 .45 mm .5 1.5 1.05 2.1 1.8 1.2165 .5 1.5 1.2 .5 5.5 1.75 .35 .5 1.591 .984 1.64 1 1 1 1 1 1 1 1 1 1 1 1 1 1 M3) 3 3 3 3 3 3 3 I :< 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Sei.945 .2 .1 .5 3 3.5 1.0157 .5 .394 .35 3.5 i.0315 .5 1.5 5.5 4 4.35 .55 .5 1.561 . .0 3.6 1.226 .25 mm 1 mm 0.35 0.5 mm 0.3 .09 .75 mm 0.54 1.06 1.5 1.08 .75 j .75 .4 1.5 1.25 .44 2.5 1.35 mm 0.42 1.5 1.5 3.0394 .52 2.25 mm 0.5 4.25 .0551 .15 3.35 .5 mm 1.315 .77 1.TABLE 14.2 .5 1. 63 .25 1.5 1.75 .8 .0 4.0 4.5 1.1575 .5 1.9 1 1.15 .125 .5 1. 0.0098 .5 .56 2.0984 .36 2.25 .83 2.57 1.: i | i I 0.6 1.787 .0 2.2 .50 1.1969 mm 0.0177 .1378 .6 1.45 mm in.709 .68 2.0217 .0 3.20 2.02 1.5 1.25 1. i/.0 2.175 .5 2.38 1.0709 .5 1.89 1.0 6 6 6 6 6 6 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 M3) 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1.0197 .2 .5 1.07 3.1772 .28 2.25 .0354 .0 5.0 1.25 0.s« «/ ouu mm mumcici Pitch Fine Coarse 6 4 mm 3 mm 2 mm 1.5 1.5 1.5 1.25 •1.5 1.5 1.footnotes at end of table.8 2 2.65 1.—HSU meine screw inreuus Size (basic major diameter) Basic major Primary Secondary Tertiary diameter JOT ytnerui use.1181 .5 4.17 2.0 1.35 .5 .6 5 5.5 1.472 .('.5 .0118 .0787 .2 .18 1.5 1.6 .5 1.10 1.75 .866 .3 .075 .25 .0138 .25 .2 1.0 6.75 2.0866 .2 0.26 1.5 1.25 1.5 6.0433 .4 .5 6 7 8 9 10 12 14 15 16 17 18 20 22 24 27 30 33 86 38 39 40 42 45 48 52 55 86 58 60 64 65 68 70 72 78 78 80 82 85 90 75 62 50 26 26 28 32 «35 11 1.4 mm 0.354 .5 3.0230 .8 2.35 .45 .2 .0630 .99 3.1. 5 1.7 .23 3.0 5.0472 .5 0.97 2. 06 9.04 10.35 mm 0.84 10. 0.65 9.25 to 300 mm diameter —Continued Pitch Basic major diameter Fine Coarse 6 4 mm 3 mm 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 mm 2 2 •i 2 2 2 2 2 2 2 2 2 1.66 8.25 of size 14 to be used only (or spark plugs.91 6.4 mm with coarse pitches shown are covered by Section V.—ISO metric screw threads for general use. 64 .83 11.87 8.92 5.86 9.68 7.13 4.61 1! SI mm mm 6 A 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 H 0 n 130 135 140 145 150 155 160 165 170 175 180 185 100 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 1 1 • Pitch 1.43 10.53 4.25 9.75 mm 0.2 mm Primary Secondary Tertiary mm 100 mm 95 105 115 120 mm no 125 in.5 mm 0.42 11. Unified miniature screw threads of Handbook 1128 (1957).74 3.02 11. ■> Pitches In parentheses not to be used unless necessary.89 7.51 5.46 8.5 mm 1.1. • Site 35 to be used (or ball bearing lock nuts.69 6. Sites 0.0» 7.72 4.63 10.22 11.12 5.48 7.25 mm 1 mm 0.27 8.31 5.10 6.TABLE Site (basic major diameter) 14.30 6.25 mm 0.3 through 1.94 4.71 5.07 8.5 9.4.24 10. 3.28 7.50 6.33 4. Part I. 0 mm 339 318 282 254 254 203 203 169 145 127 113 102 102 102 85 73 73 64 56 56 51 42 36 34 32 25 25 20 17 15 13 13 10 10 10 8 8 7 7 6 6 3.25 1.315 .1 .2 in.25 1.08 .945 1.0 2.787 .276 .4 .0709 .0138 .0 2.0551 .0118 .2 1.1378 .5 4.0157 .0 4.8 2.7 .0315 .5 2.1969 .551 . approximate Pitch Threads per inch. bolts.75 2.5 4.4 mm are covered by Section V.394 .866 .0 25 20 20 17 17 17 17 17 13 13 13 13 8 8 14 18 22 27 33 39 Sizes 0.5 2.075 .45 .7 .9 1.0787 .25 .1181 .1 1.15 .5 3 4 5 6 8 10 12 16 20 24 30 36 mm 0. 1575 .06 1.25 .175 .5 3.42 1.TABLE 14.09 .0 3.6 .75 .5 1.8 1 1.25 .0354 .S5 to 89 mm diameter Coarse Basic major diameter Fine Size (basic major diameter) Primary Secondary Pitch Threads per inch.25 .8 1.0433 .5 .0 1.5 1. approximate mm 0.5 1. 65 .35 .54 mm 0.2 .45 .630 .472 . 0.0236 .0394 .0098 .236 .0197 .225 .3 through 1.35 .0177 .5 2. 0.—ISO metric screw threads for screws.5 .30 1.5 7 i.1772 .0276 .0 2.0 3.0984 .55 .18 1.6 2 2.0866 .0630 .25 1.709 .2.5 1.4 1.4 .125 . Part I.0 2. and nuts.0 3.35 .5 3.0472 .125 .0 1.45 .0217 .3 .3 . Unified miniature screw threads of Handbook H28 (1957).6 .5 1.1 .0 3.ö 1.0 2. 60 54 47 66 U. Acme threads Buttress threads .18. leading Trailing Form of thread. lead and angle Diameter equivalent Of angle deviations Of lead deviations 46 7 32 48 62 34 45 45 21. tripod connections for Centralizing Acme threads Class 5 fit for threaded studs Classification and tolerances.. 60" stub Square. modified Stub Acme Surveying Instrument mounting Deviations. pitch diameter..60 60 52 34 38 3« 27 Lamp base and lamp holder threads Lead deviations. Buttress thread Microscope and noseplece thread Whitworth thread Buttress threads 54. Wrench openings Torque-tension relationship Torques.51 48 51 51 52 61 62 61 W Whitworth threads.. GOVERNMENT MINTING OFFICE: ItfO .. 38 69 54 54 54. ISO metric threads Microscope objective and noseplece Photographic equipment threads. measurement of Sizes of Specifications for Wrench openings. Compensation. Stub Acme threads Angle deviations. interference fit ISOmetric Lamp base and lamp holder 60° stub Square. Acme threads Stub Acme threads Load sensitive screw 34 33 32 42 42 6 20 63 M Marking of gages Measuring load Measurement of pitch diameter Metric thread standards Microscope objective and noseplece threads Multiple-start threads— _ 7.18 4 28 62 19 62 5 29 19 64 47 52 61 60 41.42 53 I Inspection. British standard Wire measurements. Acme threads Buttress threads Electric lamp base and lamp holder threads Stub Acme threads Gaging practice.22 40 33 33 33 33 Photographic equipment threads Pitch diameter.INDEX A Acme screw threads Allowances. interference fit Trailing flank Tripod connections for cameras Tru-loadbolt 1. diameter equivalent of Leading flank Lens accessory attachment threads Lens mounting threads Limits of size.38 54 54 62 36 55 Cameras.. thread. Page 46 B Best wire diameters _ Bibliography. Acme threads Stub Acme threads -. Buttress Class 5.22.S. Acme threads Stubs Acme threads 32 60 1 28 34 61 18 10 21 Oages. stud and tapped hole threads Interference fit threads Assembly torques Breakloose torques Extension of standard International metric threads ISO metric threads ISO thread profiles 48. Buttress threads General purpose Acme threads Glass buttle and Jar threads 10 33 35 25 33 1 46 H Historical. Noseplece threads 27 D Dairy sanitary fittings threads Designations. thread measuring.32.42 1 48 4 19 17 18.27 N National Buttress threads. Interference fit threads Electric lamp base and lamp holder. for adjusted gage lengths Concentricity 41. class 6 fit for 1 27 48 34 62 36 41 46 45 18 22 40 46 48 Electric lamp base and lamp holder threads 34 Flank..40 Thickness of thread Thread series.36. Acme Buttress Electric lamp base and lamp holder ISOmetric Stub Acme Formulas for diameters. modified Surveying instrument mounting Shutter cable release tip and socket Studs. Acme. modified Stub Acme Stub Acme.. measurement of Preload indicating washer Pressure flank 41 54 63 28 Rolled threads for electric lamp bases and lamp holders 34 S Screw threads.27. diameter equivalent of Page I 6 31 20 33 Jar threads. Acme thread Buttress thread Stub Acme thread Wires. Acme Buttress ISOmetric Stub Acme Tightening of threaded fasteners Tolerances. Acme Buttress Class 5. limitations on Of pitch diameter Wires. measurement of pitch diameter Tightening of threaded fasteners British standard. 1.21. Navigation Systems. Atomic Physics. High Frequency and Very High Frequency Research. Cryogenic Physics. Roof. Tropospheric Analysis. Radio Propagation Engineering. Radiation Physics. and engineering in the field indicated by its title. Plastics. Organic Chemistry. Radio Noise. Electronic Instrumentation. Radio Broadcast Service. WASHINGTON. BOULDER. In general. and Fluid Meters.. Electrodeposition. Refractories. Airglow and Aurora. Organic and Fibrous Materials. 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