TECHNICAL INFORMAtION ON FAStENERS1 1.1 1.2 1.3 1.4 1.5 1 Steel fasteners for the temperature range between 50°C and +150°C Materials for fasteners Mechanical properties of steel screws 1.2.1 Tensile test 1.2.2 Tensile strength Rm (MPa) 1.2.3 Apparent yielding point Re (MPa) 1.2.4 0.2% offset yield point Rp0,2 (MPa) 1.2.5 Tensile test on whole screws 1.2.6 Strength classes 1.2.7 Elongation at fracture A5 (%) 1.2.8 Hardness and hardness test methods Strength classes of screws 1.3.1 Test forces 1.3.2 Properties of screws at increased temperatures Strength classes for nuts Pairing of screws and nuts 1.5.1 Information for steel nuts 1.5.2 Stripping resistance for nuts with a nominal height ≥ 0.5 d and < 0.8 d (in accordance with DIN EN 20898, Part 2) Mechanical properties of threaded pins Marking of screws and nuts Inch thread conversion table inch/mm 3 3.1 3.2 3.3 3.4 3.5 ISO information technical standardisation – changeover to ISO Code 3.1.1 Product names and product changes DIN-ISO successor standards – ISO-DIN previous standards DIN-ISO changes to widths across flats Standard changeover DIN/ISO 3.4.1 Technical terms of delivery and basic standards 3.4.2 Small metric screws 3.4.3 Pins and screws 3.4.4 Tapping screws 3.4.5 Hexagon head screws and nuts 3.4.6 Threaded pins Dimensional changes to hexagon head screws and nuts Manufacturing screws and nuts Manufacturing processes 4.1.1 Cold forming (cold extrusion) 4.1.2 Hot forming 4.1.3 Machining Thread production 4.2.1 Fibre pattern Heat treatment 4.3.1 Hardening and tempering 4.3.2 Hardening 4.3.3 Annealing 4.3.4 Case hardening 4.3.5 Stress relief annealing 4.3.6 Tempering Surface protection Corrosion Corrosion types Frequently used types of coatings for fasteners 5.3.1 Nonmetallic coatings 5.3.2 Metallic coatings 5.3.3 Other coatings 1.6 1.7 1.8 2 Rust and acid-resistant fasteners 2.1 Mechanical properties 2.1.1 S trength classification of stainless steel screws 2.1.2 Apparent yielding point loads for set screws 2.1.3 Reference values for tightening torques of screws 2.2 Corrosion resistance of A2 and A4 2.2.1 Surface and degrading corrosion 2.2.2 Pitting 2.2.3 Contact corrosion 2.2.4 Stress corrosion cracking 2.2.5 A2 and A4 in combination with corrosive media 2.2.6 Creation of extraneous rust 2.3 Marking corrosion-resistant screws and nuts 4 4.1 4.2 4.3 5 5.1 5.2 5.3 1743 10 5.4 Standardisation of galvanic corrosion protection systems 5.4.1 Designation system in accordance with DIN EN ISO 4042 5.4.2 Reference values for corrosion resistances in the salt spray test DIN 50021 SS (ISO 9227) 5.4.3 Designation system in accordance with DIN 50979 5.4.4 Designation of the galvanic coatings 5.4.5 Passivations 5.4.6 Sealings 5.4.7 Minimum layer thicknesses and test duration 5.5 Standardisation of non-electrolytically applied corrosion protection systems 5.5.1 Zinc flake systems 5.5.2 Standardisation of non-electrolytically applied corrosion protection systems Designations in accordance with DIN EN ISO 10683 5.6 Standardisation of the hot-dip galvanising of screws in accordance with DIN EN ISO 10684 5.6.1 Procedure and area of application 5.6.2 Thread tolerances and designation system 5.7 Restriction on the use of hazardous substances 5.7.1 RoHS 5.7.2 ELV 5.8 Hydrogen embrittlement 6 Dimensioning metric screws 6.1 Approximate calculation of the dimension or the strength classes of screws in accordance with VDI 2230 6.2 Choosing the tightening method and the mode of procedure 6.3 Allocation of friction coefficients with reference values to different materials/surfaces and lubrica tion conditions in screw assemblies (in accordance with VDI 2230) 6.4 Tightening torques and preload forces for set screws with metric standard thread in accordance with VDI 2230 6.5 Tightening torques and preload forces for safety and flange screws with nuts in accordance with manufacturer‘s information 6.6 Reference values for tightening torques for austenite screws in accordance with DIN EN ISO 3506 6.7 How to use the tables for preload forces and tightening torques! 6.8 Pairing different elements/contact corrosion 6.9 Static shearing forces for slotted spring pin connections 6.10 Design recommendations 6.11 Assembly 7 7.1 7.2 7.3 7.4 7.5 8 8.1 8.2 8.3 Securing elements General Causes of preload force loss Methods of functioning 7.3.1 Securing against loosening 7.3.2 Securing against unscrewing 7.3.3 Securing against loss How securing elements work 7.4.1 Ineffective securing elements 7.4.2 Loss-proof fasteners 7.4.3 Loose-proof fasteners Measures for securing screws 7.5.1 Loosening 7.5.2 Automatic unscrewing Steel structures HV joints for steel structures HV screws, nuts and washers Construction information and verifications for HV joints in accordance with DIN 18800-1 and DIN EN 1993-1-8 8.3.1 HV joints in accordance with DIN 18800-1 (2008) 8.3.2 HV joints in accordance with DIN EN 1993-1-8 8.4 Assembly 8.4.1 Assembly and test in accordance with DIN 18800-7 8.4.2 Assembly in accordance with DIN EN 1090-2 8.5 Special information for using HV assemblies 1745 10 1744 Direct screwing into plastics and metals Direct screwing into plastics Direct screwing into metals 9.2.1 Metric thread grooving screws 9.2.2 Screw assemblies for thread-grooving screws in accordance with DIN 7500 9.2.3 Direct screwing into metals with threadgrooving screws in accordance with DIN 7500 9.3 Tapping screws 9.3.1 Tapping screw assemblies 9.3.2 Thread for tapping screws 10 Riveting 10.1 Rivet types 10.1.1 Solid rivets 10.1.2 Hollow rivets 10.1.3 Tubular rivets 10.1.4 Expanding rivets 10.1.5 Semi-tubular pan head rivets 10.1.6 Two-piece hollow rivet 10.1.7 Blind rivets 10.2 Instructions for use 10.2.1 Joining hard to soft materials 10.2.2 Corner clearances for connections 10.3 Definitions and mechanical parameters 10.4 Using blind rivets 10.5 Rivet nuts 10.5.1 Using rivet nuts 10.5.2 Special types of rivet nuts 10.6 Rivet screws 10.7 Troubleshooting 10.7.1 Selected grip range too large 10.7.2 Grip range too small 10.7.3 Bore hole too big 10.7.4 Bore hole too small 10.8 Explanation of terms 10.8.1 Cup-type blind rivet 10.8.2 Grip range 10.8.3 Multi-range blind rivet 10.8.4 Rivet sleeve diameter 10.8.5 Rivet sleeve length 10.8.6 Closing head 10.8.7 Setting head 10.8.8 Rupture joint 9 9.1 9.2 1745 10 060 0. 0.025 0.55 0.g. hardened and tempered or Alloy steel.050 0. Part 2: Nuts Strength class Material and heat treatment Chemical composition (molten mass analysis %)a C min.55 0. – These standards stipulate the material that is to be used.6c. The most important standards for screws and nuts are: • DIN EN ISO 898-1.55 0.13 – 0.050 0. the properties of the finished parts and their tests and test methods.003 425 0.55 0.025 0. hardened and tempered or Carbon steel.20e 0. S TEEL FAsTENERs FOR THE TEMPERATURE RANGE BETWEEN –50°C AND +150°C 1.050 S max.40 0.025 0.g. hardened and tempered or Carbon steel.g.025 0.6c 5. 0. B or Mn or Cr). not stipulated Tempering temperature °C min. nuts and fittings).025 0. hardened and temperedg 10.025 0.025 0.9f Carbon steel with additives (e.060 0. 4.20 0. B or Mn or Cr).025 0. d 4.55 0.025 0.025 0.15 0.060 0. hardened and tempered or Alloy steel. the marking. B or Mn or Cr).8d 5. Mechanical properties of fasteners made of carbon steel and alloy steel.25 0. the fastener made from it can no longer satisfy the requirements made of it.025 0. Different materials are used for the different strength classes which are listed in the following table 1.8f Carbon steel with additives (e.1 Materials for fasteners The material that is used is of decisive importance for the quality of the fasteners (screws.40 0.25 0.20 0.025 0.050 0.55 0.1. hardened and temperedg 9.55 0.003 425 Carbon steel or carbon steel with additives – max. If there are any faults in the material used.55 0. hardened and tempered or Carbon steel.025 0.025 0. 10 1746 .025 0.15e 0.25 0.15e 0. Part 1: Screws • DIN EN 20898 Part 2 (ISO 898 Part 2).55 0.025 0. hardened and tempered or Alloy steel.20 0. hardened and temperedg 0.55 P max.003 425 0.55 0.8f Carbon steel with additives (e.025 0. 0.8d 6.8d 8.025 0. Mechanical properties of fasteners.060 Bb max. In this context. hardened and temperedg Carbon steel with additives (e. g Alloy steel must contain at least one of the following alloying components in the given minimum amount: chromium 0.2% offset yield point Rp0.8 and 10. and not in the connection between the head and the shaft.003 0. and elongation at fracture A5 (%). phosphorous 0. the assembly and the operating conditions must be taken into account.025 0.9 a metallographically detectable white layer enriched with phosphorous is not permissible. i 12. yield point Re.2.11%. 0. It results from the maximum force and the corresponding cross-section. i Alloy steel. hardened and tempered 0.50 P max. If two.30%. 1.35%. The boron content may reach 0.20%. 0.50 0. h.9f. the product analysis applies. In case of cold-formed screws in strength classes 4.9 must be present in simple carbon steel with boron as an additive and a carbon content under 0. f Materials in these strength classes must be sufficiently hardenable to ensure that there is a martensite share of roughly 90% in the hardened state before tempering in the microstructure of the core in the threaded part. 0. Tensile strength on fracture in cylindrical shaft (turned off or whole screws): Rm = maximum tensile force/cross-section area = F/So [MPa] Tensile strength on fracture in thread: Rm = maximum tensile force/tension cross-section = F/As [MPa] As tension cross-section 1747 10 .9 is used.8 and 0. B or Mn or Cr or molybdenum).10%. This must be verified with a suitable test procedure. d Free-cutting steel with the following max.025 0.2. 0.30 0. a b c 1. three or four elements are ascertained in combinations and have smaller alloy shares than those given above.6 heat treatment of the wire used for cold forming or the cold formed screw may be necessary to achieve the required ductility. 1. With full strength screws the fracture may only occur in the shaft or in the thread.003 Tempering temperature °C min. 0.2 Tensile strength Rm (MPa) The tensile strength Rm indicates the tensile stress from which the screw may fracture.34%.025 S max. h In case of strength class 12. h. max.2.6 and 5.025 Bb max. lead 0. Special environmental conditions may lead to stress corrosion cracking of both uncoated and coated screws.9f. nickel 0.7% for strength classes 9. sulphur.Strength class Material and heat treatment Chemical composition (molten mass analysis %)a C min. provided that the non-effective boron is controlled by additions of titanium and/or aluminium.28 In case of arbitration. i Caution is necessary when strength class 12. A difference is made between “tensile test with turned off specimens” and “tensile test on whole screws” (DIN EN ISO 898 Part 1). molybdenum 0. vanadium 0.30%.25% (molten mass analysis).g.9/12. the threshold value to be applied for the classification is 70% of the sum of the individual threshold values given above for the two. 425 380 12.2 Mechanical properties of steel screws This chapter provides a brief overview of the methods used to stipulate and determine the mechanical properties of screws. phosphorous and lead shares is permissible for these strength classes: sulphur 0.005%.9/12. the most common parameters and rated quantities will be discussed. three or four elements concerned.6% for strength class 8.1 Tensile test The tensile test is used to determine important parameters for screws such as tensile strength Rm. e A manganese content of not less than 0. The suitability of the screw manufacturer. 6 (qualitative) Fig. Fig. C 10 1748 . Tensile test on a turned-off screw Fig.1. A Tensile test on a whole screw Fig. C shows the qualitative curve of a 4. under tensile load.2.3 Apparent yielding point Re (MPa) Under DIN EN ISO 898 Part 1 the exact yield point can only be determined on turned off specimens. It represents the transition from the elastic to the plastic range. The yield point is the point to which a material. can be elongated without permanent plastic deformation.6 screw (ductile steel) in the stress-strain diagram. B Stress-strain diagram of a screw with the strength class 4. a less complicated test of whole screws is also possible. Determining Rm: the first number is multiplied by 100.004 8 d offset yield point Rpf.2% is achieved. 1. This is determined on turned off screws with a defined shaft range (proportional rod) (exception: rust. the extension to fracture Af and the 0.6 Strength classes Screws are designated with strength classes. this test can only be used to determine the tensile strength Rm.7 Elongation at fracture A5 (%) The elongation at fracture is an important parameter for assessing the ductility of a material and is created on the load to the screw fracturing.2 represents the tension at which a permanent elongation of 0. The 0. D 1. 1.8 1.4 0.2: the first number is multiplied by the second and the result is multiplied by 10.2% offset yield point Rp0.3 of ISO 898-1 2009-08. → Re = (8 x 8) x 10 = 640 MPA.9 screw.2 (MPa) The offset yield point Rp0.and acid-resistant screws.5 Tensile test on whole screws Along with the tensile test on turned off specimens.2. 2. Fig.2. so that it is very easy to determine the tensile strength Rm and the yield point Re (or the 0. steel group A1–A5). The permanent plastic elongation is shown as a percentage and is calculated using the following equation: A5 = (Lu–Lo)/Lo x 100% Lo Defined length before the tensile test Lo = 5 x do Lu Length after fracture do Shaft diameter before the tensile test Example of a proportional rod Stress-strain diagram of a screw with strength class 10.2% offset yield point Rp0.2.2). in deviation from the test for the proportional rod. 0. Determining Re or Rp0. → Rm = 8 x 100 = 800 Mpa The first number indicates 1/100 of the minimum tensile strength in MPa. In this test. the whole screw is clamped into the test device at the head and the thread.2% offset yield point Rp0.9 (qualitative) Fig. Fig. Example: Screw 8. the result is the yield point Re or 0. E 1749 10 . because most hardened and tempered steels do not show a marked transition from the elastic into the plastic range.1.004 8 d offset yield point Rpf (MPa) in accordance with chapter 9.2. Because in this case the ratio of the length and the diameter of the specimen is not always the same. D shows the qualitative tension curve in the stress-strain diagram for a 10.2.2 is determined as a so-called substitute yield point.2% offset yield point Rp0. F: Extract from DIN EN ISO 18265 10 1750 . are shown. elongation at fracture. in which each of the properties such as tensile strength.. Representation of different hardness scales on the Vickers scale Legend: X Vickers hardness HV 30 Y1 Rockwell hardness Y2 Brinell hardness 1 2 3 a b Hardness range for non-ferrous metals Hardness range for steels Hardness range for hard metals Brinell hardness. The most important hardness test methods in practice are: Test method Vickers hardness HV DIN EN ISO 6507 Pyramid Brinell hardness HB DIN EN ISO 6506 Ball Rockwell hardness HRC DIN EN ISO 6508 Tube Comparison of hardness data The following graph F applies for steels and corresponds to the hardness comparison tables in DIN EN ISO 18265.3 Strength classes of screws The mechanical and physical properties of screws and nuts are described with the help of the strength classes. determined with hard metal tube (HBW) Fig. These should be used as a starting point.1. This is done for screws in Table 2 below by means of nine strength classes. determined with steel ball (HBS) Brinell hardness. etc.8 Hardness and hardness test methods Definition: Hardness is the resistance that a body uses to counter penetration by another. harder body.2. Specimen The test using the Vickers method comprises the complete hardness range for screws. hardness. 1. because an exact comparison of results is only possible with the same method and under the same conditions. yield point. 100 – – 970 0.91 830 – – 640 660 – – 600 0.000 1.2 min or Sp. See Annex 5. min. min. the 0. The hardness measured at the end of a screw may not exceed max.c min. MB.8 6. Spf.2. 0.nom/ReL min or Sp. min. max. min.0004 8 d offset yield point for whole screws Rpf.90 600 600 – – – – 480 480e 440 0. The values for Rpf min are examined for strength classes 4.9 d≤ d> d≤ 16 mma 16 mmb 16 mm 1 2 3 4 5 Tensile strength. max.200 1. Z. G. MPa Tension under test force. mm 15 16 17 18 a b c d e f g h 12.015 20 nach ISO 898-7 27 27 27 27 m ISO 6157-3 23 34 28 37 32 39 h.3.91 900 900 – – 720 720 – – 650 0. nom. 5. min.5 250 320 238 304 – – 22 32 h 1/2H1 0.6 4.Mechanical and physical properties of screws Strength class No. cf. HV Fracture torque.8.nom/Rpf min 6 7 8 9 10 11 12 Percentage elongation at fracture of a turned off specimen.220 – – 1. Tab.040 – – 900 940 – – 830 0.8. max. Nominal values are stipulated only for the designation system of the strength classes. Mechanical or physical property 4.14. A. MPa 0.c min.2% offset yield point Rp0.94 420 – – – – 320 340e 310 0. HRC 13 14 Surface hardness.3 Height of non-decarburised thread zone. 250 HV.88 nom. m Values for KV are examined. 2: Extract from DIN EN ISO 898-1. nom. max. Af (see Annex C as well) Head impact strength Vickers hardness. 120 220g 114 209g 67 95. Nm Notch impact energy. The current values are shown only for the calculation of the test stress ratio.nom/Rp0.080 1. min.i 2/3H1 39 44 h. max. They are not test values. KVk. i An increase of the surface hardness to over 390 HV is not permissible.2% offset yield point Rp0.92 800 800 – – 640 640 – – 580 0. MPa 0. J Surface condition in accordance with Values do not apply to steel construction screws.9/ 12.8 8. if both the surface hardness and the core hardness are determined with HV 0.93 520 – – – – 400 420e 380 0.0g – – – – – – – – ISO 6157-1n 27 – 71 79 82 124 147 152 130 155 160 190 250 181 238 89 99. 400 400 240 240 – – – – 225 0.8 and 6. min. l.88 min. % Percentage contraction at fracture of a turned off specimen. HBW F = 30 D2 Rockwell hardness. 238 HB or 99.j 3/4H1 255 335 242 318 290 360 276 342 320 380 304 361 385 435 366 414 Loss of hardness following re-tempering (hardening). E. max.20 – – – No fracture min.22 0. l Applies for d ≥ 16 mm.9 1.2 may be determined. % Extension to fracture of a whole screw. k The values are determined at a test temperature of −20°C.8 5.5 HRB. HRB Rockwell hardness.90 1.8 9.8 10. 22 – – – 20 – – 12 52 12 10 48 9 48 – 8 44 – 0. If the lower yield point ReL cannot be determined.24 – 0. MPa Test resistance ratio Sp. mechanical and physical properties of screws 1751 10 . n ISO 6157-3 may apply instead of ISO 6157-1 by agreement between the manufacturer and the customer. mm Depth of complete decarburisation in the thread.c min. Rm. HV. MPa Lower yield point. min. 9. Test forces are stipulated in tables 5 and 7.91 500 500 300 300 – – – – 280 0. HV F ≥ 98 N Brinell hardness. ReLd. max. j An increase of the surface hardness to over 435 HV is not permissible. For steel construction screws d ≥ M12. nom. The surface hardness at the respective screw may not exceed 30 Vickers points of the measured core hardness.6 5. nom.c min. 000 342.9 36.000 303.000 126.000 238.230 11.000 381.000 147.900d 54.860 5.410 2.580 8.700c 37.900 35.000 947.6.940 3.400 10.000 If a thread pitch is not indicated in the thread designation.600 32.100 21.200c 22.100 16.500 28.000 174.1 28.900 84.000 445.250 8. Test forces for ISO metric standard thread 10 1752 .980 3.000 586.130 1.78 14.200c 23.100 1.6 5.290 9.460 4.100c 56.000 Test force.000 273. The test is regarded as successful if the screw length after measuring coincides with the length before the test.800 95.600 11. See 9.600 93.000 84.000 416.720 2.800 76.000 37.530 1.000 212.800 3.000 152.640 8.100 23. A tolerance of ±12.880 6.500 59.410 5.000 253. the standard thread is stipulated. N 1.910 2.200 4.000 337.000 466.nom.000 305.3.000 128.000 26.000c 18.000 220. Annex A.700 16.8 10.270 4.000 12.100 108.920 2.800 19.230 7.630 8.980 3.900 16. ISO metric standard thread Threada d Nominal tension cross-section t As.000 673.500 115.500 53.800 142.400c 35.980 6.000 294.200c 13.000 429.1.000 215.100 5.000 810.000 133.580 2.5 μm applies.500 1.000 – 159.000 112.000 130.2 20.000 68.000d 102. reduced values apply for screws with thread tolerance 6az in accordance with ISO 965-4 that are to be hot-galvanised.000 359.9 12.400 103.960 8.800 109. The following tables are an important help for the user for choosing suitable screws.000 93.000 174.800 13.000 73.210 2.800 24.300 19.1.100 91.340 3.520 6.000 792.700 50.6 4.100 48.230 5. mm2 5.180 4.000 275. 68800 N (for M14) and 94500 N (for M16).000 35.710 7.900 2.5 M4 M5 M6 M7 M8 M10 M12 M14 M16 M18 M20 M22 M24 M27 M30 M33 M36 M39 a b c d 8.1 Test forces In the tensile test the test force shown in tables 3 and 4 is applied axially to the screw and held for 15 s.000 184.000 371. 3: Extract from DIN EN ISO 898-1.000 43.6 58 84.000 544.000 490.800 70.000 264.800 25.8 9.000 81.8 6. nomb.600 66.9/ 12.000 98.700d 74.3 115 157 192 245 303 353 459 561 694 817 976 Strength class 4.600 32.100 68.000 25.240c 11.000 229.9 4.000 576.03 6. nom × Sp).700 48.630 5.200 79.000 115.700 18.700 69.000 156.000 134.500 33.000 157.000 186.800 30.200 48.700 44.000 202.000 252.560 1.840 11.000 M3 M3.78 8.000 182.090 1.000 293.000 678. For steel construction screws 50700 N (for M12).000 194.000 – – – – – – – – 203.200 55. Tab.8 8.000 155.500 13. In accordance with ISO 10684:2004.1 for the calculation of As.000 310.000 247.000 16.000 59.000 213.8 5.400 3.520 13.300 43.400 6. Fp (As. 100 + 100 °C 250 590 875 1.500 55.300 26.25 61.100 14.2% offset yield point Rp 0.000 154.6 5.000 93.000 218.200 104.600 25.820 12. mm2 Test force.600 67.500 61.500 39.9/ 12.000 329.000 – 226.400 81.000 289.000 618.300 76.500 89.8 10. nom × Sp).000 412. 5: Extract from DIN EN ISO 898-1 1999-11.500 28.500 38. The strength class of a nut is described through a test stress in relation to a hardened test mandrel and divided by 100.500 53.800 19.400 37.000 481.000 171.800 27.2 M10 x 1.800 28.000 264.000 632.100 38. Up to the test forces shown in table 6 a tensile load on a screw is possible without problems (take note of pairing 1.000 839.000 6.000 319.000 515.020 + 200°C 210 540 790 925 + 250°C 190 510 745 875 + 300°C 160 480 705 825 Lower yield point ReL or 0. N 8.000 718.000 288.100 95.5).000 146.400 33.000 139.000 60.200 22.100 59.8 10.000 174.000 273.000 126.000 112.000 242.9 300 640 940 1.900 17.000 17. Test forces for ISO metric fine thread 1.5 M12 x 1.700 23.000 72.5 125 M16 x 1.700 20. Example: M6. Fp (As. the test stress and the test forces calculated from it are usually indicated as parameters (04 to 12).2 MPa Tab.000 13.500 32.000 335.8 9.000 188.000 372.030 14. because the yield point does not have to be stated.000 210.800 46.000 162.000 163.000 a See 9.9 38.100 19.600 51.200 84.000 18.000 140.900 35.000 268.400 62. They are not intended for the acceptance test of screws.8 cross-section t As.6.000 298.000 453.000 103.000 738.6 4.900 76.000 213.800 41.5 M22 x 1.000 – – – – – – – 276.000 40.5 88.000 519.900 53.000 381.000 855. 4: Extract from DIN EN ISO 898-1.800 51.000 602.000 373. hot yield strength 1.1 for the calculation of As.000 37.000 323.000 192.3.8 5.1.000 130.000 319.nom Tab.8 8.000 M8 x 1 39.300 73.500 63.300 121.200 11.000 139.000 169.000 – 179.700 28.2 Properties of screws at increased temperatures The values shown apply only as an indication for the reduction of the yield points in screws that are tested under increased temperatures.5 M24 x 2 M27 x 2 M30 x 2 M33 x 2 M36 x 3 M39 x 3 167 216 272 333 384 496 621 761 865 1.2 M10 x 1 64.500 24.000 457.Metric ISO fine thread Thread dxP Nominal Strength class tension 4.5 M20 x 1.800 35.000 232.000 391.100 35.500 20.25 92.9 12.1 M12 x 1.800 50.4 Strength classes for nuts With nuts.6 8.400 119.500 96.300 24.900 103.000 25.000 230.000 236.9 12.000 108.000 120.700 85.000 195. Strength class Temperature + 20 °C 5.500 73.000 59.200 86.000 200.800 48.500 57.400 47.900 82. nomb.1 M14 x 1. test stress 600 MPa 600/100 = 6 strength class 6 1753 10 .200 74.000 109.5 M18 x 1.000 146.000 236.000 999. 100 594.100 353.910 2. Note: In general nuts in the higher strength class can be used instead of nuts in the lower strength class.1 28.900 868.78 8.700 – 115.5 1.800 7.100 176.200 324.500 – 51.000 154.200 39.500 – 93. To avoid the danger of stripping threads when tightening with modern assembly technology methods.400 73.400 7.250 7.5 Pairing of screws and nuts: Rule: If a screw has strength class 8.500 154.5 4 4 1. where: d2 is the flank diameter of the external thread (nominal size) d3 is the core diameter of the production profile of the external thread (nominal size) d 3 = d1 – H 6 with d1 Core diameter of the base profile of the external thread H = height of the profile triangle of the thread 1.000 42.03 6.800 16.500 – 2.500 190.000 97.100 7.000 – 3.550 4.580 3.700 638.050 5.5 2.0 84.700 514.050 7.900 138.100 67.200 16.500 234.800 19.300 120.800 374.800 980.100 289.700 78.200 80.500 12.3 115 157 192 245 303 353 459 561 694 817 976 Strength class 04 05 4 5 6 8 9 10 12 Test force (AS × Sp).800 109. This is advisable for a screws-nut connection with loads above the yield point or above the test stress (expansion screws).150 10.400 30.200 34.400 403.5 M4 M5 M6 M7 M8 M10 M12 M14 M16 M18 M20 M22 M24 M27 M30 M33 M36 M39 0.9 36.200 280.700 186.000 – 370.000 14.000 222.900 1.550 422.100 26.500 101.100 122.200 – 59.200 164.100 – 7.550 5.200 – 134.900 33.000 74.000 138.400 24.200 – 4.100 13.400 – 5.400 – 3.7 0.6 0.2 20.200 499.200 832.100 225.500 – 213.700 7.000 96.400 176.700 – 21.600 3.500 735.300 109.600 203.340 4.100 41.000 10.700 42.900 488.100 32.800 321.600 170.035.200 – 43.78 14.500 – 149. In addition.400 59.400 259.500 – 230.800 314.Test forces for ISO metric standard thread (nuts) Thread Thread pitch Nominal stressed cross section of the test mandrel As mm2 5.200 – 16.500 60.700 638.700 588.500 – 13.700 347.25 1.600 727.000 497.500 286.300 18.400 50.8.000 363.000 29.900 22.8 1 1 1.5 0.900 18.600 897.500 416. N – – Style 1 Style 1 Style 1 Style 1 Style 2 Style 2 Style 1 Style 1 Style 2 mm M3 M3.900 176.700 897.400 1.900 70. a screw assembly of this type is fully loadable.500 408.400 229.600 – 310. Test forces for ISO metric standard thread (nuts) The test force FP is calculated as follows with the help of the test stress Sp (DIN EN 20898 Part 2) and the nominal stressed cross section As: Fp = As x Sp The nominal tension cross-section is calculated as follows: p d2 + d 3 2 As = 2 4 nuts have to be paired in accordance with the above rule.900 121.700 13.500 17.900 218.400 20.250 9.200 278.000 353.300 – 22.600 550.900 183.5 3.200 751. 6: Extract from DIN EN 20898-2.500 5.000 4.900 516.300 408.400 225.600 24.100 751.700 – 263.300 66.900 9.600 100.800 95.700 278.000 14.600 866.200 330.100 499.400 254.800 6.140 – 11.200 324.400 38.900 437.500 125.200 5.300 80.600 136.100 151.900 23.640 10.000 – 32.800 673.800 134.700 5.000 – 11.900 31.600 423.800 269. screws and 1754 10 .100 88.700 57.5 2.200 – 174. a nut with a strength class 8 has to be chosen as well.500 180.300 516.171.200 176.500 54.6 58.800 614.000 – 8.75 2 2 2.000 Tab.400 – 4.5 3 3 3.500 617.500 422.500 98.000 – 294.300 486.800 – 34.900 702.400 218.200 – 2. 1 Information for steel nuts A screw in strength class 8. 1755 10 . 1. 22H – this is not the case.8 D) Strength class of the nuts 4 5 6 8 9 10 12 Appropriate screw Strength class 3.5.8 10.6 5. Minimum stress in the screw before stripping when paired with screws in strength classes in N/mm2 6.5 d and < 0. Part 2) If nuts are paired with screws in a higher strength class.8 300 370 10.9 350 480 Tab.5.8 and a nut in accordance with DIN 934 (nominal height approx. 7: Extract from DIN EN 20898 Part 2 1.Pairing of screws and nuts (nominal heights ≥ 0. this connection is not to be loaded with certainty to the screw’s yield point. nuts with hardness details 14H. Strength class of Test stress the nuts of the nuts N/mm2 04 05 380 500 1. 05.6 5.6 3. When a screw in strength class 8.8 260 290 8. I12I. I6I. the screw can be loaded to the yield point. The reference value show here for the stripping resistance refers to the strength class shown in the table.9 12.9 330 410 12. stripping of the nut’s thread can be expected. To mark and differentiate them.8 4.8 Thread range > M16 ≤ M16 ≤ M39 ≤ M39 ≤ M39 ≤ M16 ≤ M39 ≤ M39 ≤ M39 ≤ M39 – ≤ M39 ≤ M16 – > M16 ≤ M39 ≤ M16 – ≤ M39 Nuts Style 1 Thread range > M16 ≤ M39 – – Style 2 Tab.8 d (in accordance with DIN EN 20898. I9I.9 4.6 4. 8: Extract from DIN EN 20898 Part 2 There is limited loadability as well for nuts in accordance with DIN 934 that are marked I8I. I10I.8 x d) are used.8 4. There are test forces for these nuts in accordance with DIN EN 20898-2.8 9. and I4I.6 Mechanical properties of threaded pins (in accordance with DIN EN ISO 898. 0. I5I. Part 5) The mechanical properties apply for threaded pins and similar threaded parts not subject to tensile stress that are made of alloyed and unalloyed steel. these nuts are marked with a bar before and after the “8” (I8I) instead of just “8”. Thanks to this connection.6 6. If nuts with a limited loadability are used – for example in strength class 04.8 8.8 is paired with a nut in strength class 8 or higher.2 Stripping resistance for nuts with a nominal height ≥ 0. 8 and a thread diameter of d ≥ 5 mm. max. max. Fig.Mechanical property Vickers hardness HV Brinell hardness HB. max.3 1) Strength class1) 14H min. max. min.7 Marking of screws and nuts Marking screws with full loadability Hexagon head screws: Marking hexagon head screws with the manufacturer’s mark and the strength class is prescribed for all strength classes and a nominal thread diameter of d ≥ 5 mm. min. 22H and 33H do not apply to threaded pins with a hexagonal socket Tab. 9: Extract from EN ISO 898-5 1. Socket head cap screws: Marking socket head cap screws with the manufacturer’s mark and the strength class is prescribed for strength classes ≥ 8. H: E xample for the marking of socket head cap screws Fig. F = 30 D2 Rockwell hardness HRB Rockwell hardness HRC Surface hardness HV 0. G: E xample for the marking of hexagon head screws 10 1756 . 140 290 133 276 75 105 22 H 220 300 209 285 95 30 320 33 44 450 45 53 580 33 H 330 440 314 418 45H 450 560 428 532 Strength classes 14H. min. The screw must be marked at a point where its shape permits. 9 2.4 4″ 102.3/4″ 69. Hexagonal nuts must be marked on the bearing surface or on a flat with a recessed mark or on the chamfer with a raised mark.2 3.7 2. e.8 Number of threads per 1″ UNC/UNF 0-inch Thread pitch UNC Thread pitch UNF 1/4″ 20 28 5/16″ 18 24 3/8″ 16 24 7/16″ 14 20 1/2″ 13 20 5/8″ 11 18 3/4″ 10 16 Tab.3 1. 10: Extract from EN 20898-2 Marking screws with reduced loadability Screws with reduced loadability have an “0” before the strength class mark. 11: Thread pitch UNC/UNF 1757 10 .2 7/8″ 22.1/4″ 57.1/2″ 38.8” and “088” are possible.8 7/16″ 11.1 5/16″ 7.1 1/2″ 12. I: E xample of marking with the code number of the strength class Marking of hexagonal nuts with the manufacturer’s mark and the strength class is prescribed for all strength classes and with a thread ≥ M5. The point between the digits may be omitted so that the variants “08. Raised marks may not project beyond the nut’s bearing surface.5 2″ 50.3/4″ 44. 1.9 1″ 25.9 1.8.1 3″ 76.1/2″ 63. This marking is possible for all strength classes.g.9 3/4″ 19.5 5/8″ 15. 8.8 Inch thread conversion table inch/mm Inch mm Inch mm 1/4″ 6.5 3/8″ 9.0 1.1 2.1/4″ 31.1/2″ 88. marking can also be done with the help of the clockwise system (for more information see DIN EN 20898 Part 2). 8 8 Fig.Marking nuts Strength class Mark 04 04 05 05 4 4 5 5 6 6 8 8 9 9 10 10 12 12 Tab. As an alternative to the marking with the code number of the strength class. 12 0.1 Mechanical properties DIN EN ISO 3506 applies to screws and nuts made of stainless steel.08 0.75–2.045 0. The steel groups and the strength classes are designated with a four-character sequence of letters and digits.03 0.08 0. There are a great number of stainless steels.045 S 0.03 Cr 16–19 15–20 17–19 16–18.5 2 2 2 2 P 0.7 – – 2–3 2–3 Ni 5–10 8–19 9–12 10–15 10.2.5 16–18.35 0.05 0. strain-hardened Steel group Austenite Martensitisch Ferrite Steel grade A1 A221 A3 A423 A5 C1 C4 C3 F1 Strength classes screws.25 4 1 4 1 A3 and A5 stabilised against intercrystalline corrosion through adding titanium.045 0.5–14 Cu 1.03 0.03 0. Chemical composition of austenite steels (in accordance with ISO 3506) 10 1758 . nuts type 1 Lower nuts 50 025 Soft 70 035 Coldformed 80 040 Highstrength 50 025 Soft 70 035 110 50 70 035 80 040 45 020 Soft 60 030 Coldformed 055 025 Soft Hardened and tempered Hardened Hardened and and tempered tempered Differentiation characteristics of austenite steel grades (in accordance with ISO 3506) Steel group A1 A2 A3 A4 A5 Chemical composition in % (maximum values.5 Mo 0.08 Si 1 1 1 1 1 Mn 6. unless other details provided) C 0. Example: A2–70 A Austenite steel 2 Alloy type in group A 70 Tensile strength not less than 700 MPa.15–0. RUST AND ACID-rESISTANT FASTENErS 2. ferrite and martensite.1 0. which are classified in the three steel groups austenite. niobium or tantalum. whereby austenite steel is the most widespread.2 0. 0 17. steels of this grade have lower corrosion resistance than corresponding steels with a normal sulphur content.4541 1. tantalum.0 2.5 ÷ 13.07 1.0 ≤ 0.35 – – – Ti ≥ 5 X % C – – Ti ≥ 5 X % C ≤ 0. possibly niobium. because this steel grade was devel oped for boiling sulphuric acids (which is the reason for the designation “acid-resistant”).03 1.0 17.4305 1. Steel grade A2 Grade A2 steels are the more commonly used stainless steels. Because of the high sulphur content.07 1.5 16. with the properties of A2 steels (stabilised against intercrystalline corrosion.0 17. e. Steels of this steel grade are not suitable for use in non-oxidising acids and media containing chloride.5 2.0 ≤ 0. and are suitable to a certain extent for environments containing chloride.0 2.0 ÷ 20.10 1.4301 1.5 Ni % 8 ÷ 10 8.5 ÷ 18.5 ÷ 18. e.4404 C % Si ≤% Mn ≤% 2.4303 1. after welding).0 ≤ 0.g.5 10.5 11 ÷ 14 10.0 ÷ 20.0 ÷ 2.0 ÷ 19. 15: Common stainless steels and their chemical composition Steel grade A1 Steel grade A1 is intended in particular for metal-cutting.5 Mo % – – – – – 2.g.0 ≤ 0.10 1.0 ÷ 19. Steel grade A3 Grade A3 steels are stainless steels stabilised through the addition of titanium.15 ÷ 0.0 2. 1. The mechanical strength values in Table 17 below are to be used for the construction of screw assemblies made of austenitic steel.5 ÷ 10 10 ÷ 12.0 Cr % 17. 1759 10 .0 ≤ 0.5 ÷ 12 9.5 10.03 1.5 2. They are used for kitchen equipment and for apparatus for the chemical industry.5 ÷ 13.4571 Tab. in case of increased corrosion loads chromium-nickel steels from steel grade A4 are used.0 16. A4 steels are used in large volumes in the cellulose industry.0 ÷ 20. Steel grade A5 Grade A5 steels are stabilised “acid-resistant steels” with properties of grade A4 steels (see A3 as well).0 2.1.0 ≤ 0.0 ≤ 0.0 ÷ 11. in swimming pools and in sea water.The most important stainless steels and their composition Material name A1 A2 X 8 Cr Ni S 18-9 X 5 Cr Ni 1810 X 2 Cr Ni 1811 X 8 Cr Ni Ti 19/10 A3 A4 A5 X 6 Cr Ni Ti 1811 X 5 Cr Ni Mo 1712 X 2 Cr Ni Mo 1712 Material no.10 1. In contrast.0 ÷ 2.4401 1.5 Altri % S 0.0 2.0 ÷ 2.5 ÷ 18. Steel grade A4 Grade A4 steels are “acid-resistant steels” that are molybdenum alloyed and have much better corrosion resistance.0 X 6 Cr Ni Mo Ti 1712 1.4306 1.0 17.1 Strength classification of stainless steel screws DIN EN ISO 3506 puts together the steel grades that are recommended for fasteners.07 1. A4 steels are also used frequently in the food industry and in ship building.5 16.0 2. 2. Austenitic steels in grade A2 are used primarily.0 2. sulphur (S). cf. 2) According to 6. A2. Stainless steels contain at least 16% chromium (Cr) and are resistant to aggressive oxidising media.250 114.3 d Austenitic A1.g. 16: Extract from DIN EN ISO 3506-1 The yield point Rp0.450 74. A higher yield point can only be achieved through strain hardening that arises as a consequence of cold forming (e.390 9.685 12. They must be marked with the steel grade and strength class in accordance with this table.750 140. Table 17 shows apparent yielding point loads for set screws in accordance with DIN EN ISO 3506.2% offset yield point Rm1) MPamin. Tab.250 2.650 110.390 117.g. molybdenum (Mo). the elongation at fracture is to be determined at the respective length of the screw and not on turned off specimens.220 7. Magnetisation through strain hardening can go so far that the steel part sticks to a magnet.4 d 0.130 96. e.2. Rp 0.700 32. A3.045 16.1. this does not affect the corrosion resistance.470 26. Nominal diameter Strength class M5 M6 M8 M10 M12 M16 M20 M24 M27 M30 Apparent yielding point loads for austenitic steels in accordance with DIN EN ISO 3506 A2 and A4 in N 50 2. improve the corrosion resistance.Mechanical properties of screws in the austenitic steel groups Steel group Steel grade Strength class Diameter range Screws Tensile strength 0.970 51.100 37.3 Reference values for tightening torques for screws.810 70 6.2 is determined in accordance with DIN EN ISO 3506-1 in the tensile test of whole screws because the strength properties are achieved in part through cold forming. Under the effect of oxygen stainless steel forms a stable oxide layer (passive layer). but a certain amount of magnetisability may be present after the cold forming.6 2.935 70.4.21) MPa min. However. Other alloy components are added only to improve the mechanical properties. nitrogen (N).g. d is the nominal diameter.2 Apparent yielding point loads for set screws Austenitic chromium-nickel steels cannot be hardened. Higher Cr contents and additional alloy components.980 4. 17: Apparent yielding point loads for set screws in accordance with DIN EN ISO 3506 10 1760 .2 Corrosion resistance of A2 and A4 Stainless steels and acid-resistant steels such as A2 and A4 come in the category of “active” corrosion protection. titanium (Ti) or niobium (Nb). 500 700 800 210 450 600 Elongation at fracture A2) mm min.1. chapter 6. Fasteners made of austenitic steels are generally not magnetisable. 0.250 88. This passive layer protects the metal from corrosion.180 17. e. A4 and A5 50 70 80 ≤ M39 < M243) < M243) The tensile stress is calculated in relation to the tension cross-section (see annex A or DIN EN ISO 3506-1). round die thread rolling). 1) Tab. 2. such as nickel (Ni). or the machining capability. These additives also influence the mechanical properties. 3) In case of fasteners with a nominal thread diameter d > 24 mm the mechanical properties must be agreed between the user and the manufacturer.6 d 0. e. through rubber. As an example. On the basis of laboratory experiments manufacturers have published resistance tables that provide information on the behaviour of the steel grades at different temperatures and concentrations in the individual media (see chapter 2. so that a contact current cannot flow.It should be noted that in practice there are a number of different types of corrosion.1–1.2. The influence of the temperature is considerable here.4 Stress corrosion cracking This type of corrosion usually occurs in components used in industrial atmospheres that are under heavy mechanical tensile and bending loads.2. The passive layer is penetrated locally here. 22 a Surface degrading corrosion. Austenite steels in atmospheres containing chloride are particularly sensitive to stress corrosion cracking. avoid unequal material pairings. chapter 6.1 Surface and degrading corrosion With uniform surface corrosion. J as examples: be the starting point for pitting. Classification of the degree of resistance into different groups Degree of resistance A B C D Assessment Fully resistant Practically resistant Less resistant Not resistant Weight loss in g/m2h < 0. 1761 10 . • Where possible.1 0. The baser element is attacked and destroyed. This type of corrosion can be prevented through a careful selection of the material. plastics or coatings.0 1.0–10 > 10 Tab. Austenitic steels such as A2 and A4 are more resistant to pitting than ferrite chromium steels. pitting b Contact corrosion c Stress corrosion cracking d Mechanical effects Fig. The following points should be observed to prevent contact corrosion: • Insulating the metals at the contact point.2 Pitting Pitting is seen through surface corrosion degrading with the additional formation of cavities and holes.2. For this reason. residues and deposits must be cleaned regularly from all fasteners. Internal stresses created by welding can also lead to stress corrosion cracking. 2. → cf.3 Contact corrosion Contact corrosion occurs when two components with different compositions are in metallic contact with each other and there is moisture in the form of an electrolyte.8 as well 2. The more frequent types of corrosion involving stainless steel are shown below and in the following Fig. Deposits and rust can also 2. the surface is degraded evenly. The critical temperature is 50°C.2. K: The most frequent corrosion types with screw assemblies 2. nuts and washers should be matched to the connecting components.g. • Make sure that the connection is not in contact with electrolytic active means. In case of stainless steel in contact with active media containing chloride there is also pitting by itself with pinhole notches in the material.5). also known as degrading corrosion.2. screws. 2.2% 2% Temperature in °C 20 boiling all 20 boiling all all all all 20 98 – 20 all all 20 boiling 20 boiling all 20 boiling all – all 20 20 all 150 180 200–235 20 boiling all all 20 50 20 50 20 Degree of resistance Degree of resistance A2 A4 A A A A A A A A A A A A A D A A C B D A A C A A A A A A A B C A B A A B C D D D A A A A A A A A A A A A A D A A B B D A A B A A A A A A A A A A A A A B B D D D 10 to 10% 1762 . Overview of the chemical resistance of A2 and A4 screws Corrosive agent Acetic acid Acetone Ammoniac Beer Benzene.) Ethyl alcohol Ethyl ether Fatty acid Formic acid Fruit juices Glycerine Hydrochloric acid to 10% 50% – – all – all – technical 10% – conc.5 A2 and A4 in combination with corrosive media The following table provides an overview of the resistance of A2 and A4 in combination with various corrosive media.2. damp gas Chloroform Chromic acid Concentration 10% all all – – all – – – – – all 10% pure 50% pure Citric acid Copper acetate Copper nitrate Copper sulphate Developer (photogr. The values shown are intended only as reference points but still provide good possibilities for comparisons. all types Benzoic acid Benzol Blood Bonderising solution Carbon dioxide Chloride: dry gas. 0. 5% 10% – approx. 26% – – all – to 40% 50% 90% Temperature in °C 20 – all 20 boiling 20 all to 50 all all all all 20 boiling 20 boiling all 20 boiling boiling all boiling boiling 20 boiling 20 boiling 20 boiling all 20 20 all 20 boiling 120 all all all 100–500 900 B boiling to 70 boiling 20 > 70 20 70 all 20 all Degree of resistance Degree of resistance A2 A4 A A A A C A A A A A A A A B A C A B C D A B A A C B D B D A A A A A B C A A A C D A B B C B B C C D A A A A A A A A A A A A A A A B A C A A C C A A A A B A C A D A A A A A B C A A A A C B A C A B B C D A A Oils (mineral and vegetable) Oxalic acid Petroleum Phenol Phosphoric acid – 10% 50% – pure 10% 50% 80% conc.5% 5% 10% 60% Sulphurous acid Tannic acid aqueous solution all 1763 10 . 1% – – cold saturated 20% 50% – 10% – – to 70% 2. Potassium permanganate 10% Salicylic acid Seawater Sodium carbonate Sodium hydroxide Sodium nitrate Sodium perchlorate Sugar solution Sulphur dioxide Sulphuric acid.Corrosive agent Hydrocyanic acid Industrial air Lactic acid Lemon juice Magnesium sulphate Mercury Mercury nitrate Methyl alcohol Milk of lime Nitric acid Concentration – – 1. Corrosive agent Tar Tartaric acid Concentration – to 10% over 100% to 50% 75% Temperature in °C hot 20 boiling 20 boiling boiling 20 and hot Degree of resistance Degree of resistance A2 A4 A A B A C C A A A A A C C A Wine – 2. If these places are not cleaned and removed. or grinding dust. • Flying sparks during work with a right angle grinder. • Water containing rust dripping onto a stainless steel surface. or during welding work.2. the rust can cause electrochemical pitting corrosion even in stainless steel. 10 1764 . Extraneous rust can be caused by: • Contact of objects that rust with a stainless steel surface. • Use of tools that were previously used to work on carbon steel.6 Creation of extraneous rust Extraneous rust consists of adherent particles of a carbon steel (“normal steel”) on the stainless steel surface that turn into rust through the effect of oxygen. g. Marking on a single flat is permissible and may only be recessed. the marking should be on the screw head.3 Marking corrosion-resistant screws and nuts The marking of corrosion-resistant screws and nuts must contain the steel group. Marking on the flats is also permissible as an option. Where possible. low cylinder heads A2 Fig. L: Extract from DIN EN ISO 3506-1 2.3) Fig. e. XYZ XYZ A2-50 Strength class only with low-strength nuts (see chapter 3. Marking nuts in accordance with DIN EN ISO 3506-2 Nuts with a nominal thread diameter from 5 mm must be clearly marked in accordance with the classification system. the strength class and the manufacturer’s mark.Origin mark XYZ XYZ A2-70 A2-70 Alternative marking for socket head cap screws XYZ A2-70 XYZ A4 Steel group Strength class A2-70 XYZ Marking of screws that do not satisfy the requirements for tensile or torsion strength because of their geometry. Marking screws in accordance with DIN EN ISO 3506-1 Hexagon head screws and socket head cap screws from nominal diameter M5 must be clearly marked in accordance with the classification system. M: Extract from DIN EN ISO 3506-2 1765 10 .2. ISO iNFoRMATioN oN TECHNiCAL sTANDARDisATioN – CHANGEoVER To ISO 3. During the harmonisation of the individual standards codes some titles are in fact being changed. This work of harmonisation in Germany was previously carried out by the Deutsches Institut für Normung e.1 Product names and product changes In many cases the introduction of the European standards is described as intransparent or even chaotic. this naming system was abandoned some years ago and replaced by the now common form “DIN EN ISO …”. there are European standards (EN standards). etc.1995 (EU/EEC). because they were introduced at a time at which the “changeover to ISO” was not yet current. However. the sooner we will profit from overcoming barriers to trade or procurement within Europe. whereby ordering the necessary components is considerably simplified. Its aim is to stipulate. European standards (EN) aim at harmonising technical regulations and statutes in the internal European market. In addition. in the area of engineering. In this way. For an interim period the number 20000 was added to the ISO number on the takeover of ISO standards into the European code (EN) (e.1 Code Technical standardisation is work of harmonisation in the technical field that is carried out jointly by all interested parties. a changeover from “DIN to ISO” is. the national standard is given the same title as the corresponding ISO standard. Following Europeanisation there are absolutely no changes to what is certainly the most important standard for screws and nuts. which are issued by the International Organisation for Standardisation. As already stated. because these have to be changed in the short or long term.. optimum solutions are found for all types of constructions. According to the task and goal of the ISO. International standards (ISO).g. DIN EN ISO 24034). EN standards are to be transposed and introduced without delay and without amendment as national standards in the Member States – and the corresponding national standards are to be withdrawn in the same step. (DIN) on the national level. for example. procedures. National standards (DIN) are being or have already been largely replaced by international/European standards. the contents of many DIN standards already conform to the ISO standard. If an ISO standard is taken over into national standards codes without change. strictly speaking. In principle. according to a decision of the European Council. ISO 898-1 “Mechanical properties of fasteners”. existing ISO standards are to be taken over as far as possible unchanged as EN standards. 3. which was realised on 1. not correct. because in the past many DIN standards had already been taken over by ISO standards. There will be DIN standards only for products for which there are no ISO or EN standards. In many cases. An ISO nut is thus known as an ISO 4032-M12-8 all over the world. However. because this standard was taken over into the German standards code from the start without any changes to the contents. which was established in 1946. It is certain that the changes to names are very annoying with regard to production documents or order data.3. and on an international level there are the ISO standards. But we have to be clear about one thing: the sooner we realise conformity to European standards. but there are not many changes to the products themselves. these are intended to serve the global harmonisation of technical rules. The old DIN standards were changed into new ISO standards. 1766 a closer look reveals that this is not the case. Many DIN standards were the foundation for ISO standards. arrange and harmonise terms.V. products.1. 10 . The difference between ISO and EN standards is that. and thus to simplify the exchange of goods and to break down barriers to trade.1. the connection would no longer be safe against failure. following more recent technical findings the ISO has changed the height of hexagonal nuts because it was recognised that the stripping resistance can no longer be guaranteed. Screws and nuts with dimensions M10. and with regard to the technical properties. This means. for example. M12 and M14 are affected (here the width across flats is reduced by 1 mm) and M22 (width across the flats is 2 mm larger). All that is 3. In contrast.8 is dimensionally. In this case.2 DIN-ISO successor standards DIN 1 7 84 85 94 125 125 126 417 427 433 438 439 439 440 551 553 555 558 601 603 660 661 911 912 913 914 915 916 ISO 2339 2338 1207 1580 1234 7089 7090 7091 7435 2342 7092 7436 4035 4036 7094 4766 7434 4034 4018 4016 8677 1051 1051 2936 4762 4026 4027 4028 4029 DIN 931 933 934 934 960 961 963 964 965 966 ISO 4014 4017 4032 8673 8765 8676 2009 2010 7046 7047 DIN ISO necessary here is a change to the name in the production documents or order files.8. Apart from these four dimensions. that a DIN 933 M16 x 50-8. particularly when modern tightening methods are used. ISO-DIN previous standards ISO ISO 1051 1207 1234 1479 1481 1482 1483 1580 2009 2010 2338 2339 2341 2342 2936 4014 4016 4017 4018 4026 4027 4028 4029 4032 4034 4035 DIN 660/661 84 94 7976 7971 7972 7973 85 963 964 7 1 1434 427 911 931 601 933 558 913 914 915 916 934 555 439 ISO 4036 4161 4762 4766 7040 7040 7042 7042 7045 7046 7047 7049 7050 7051 7072 7089 7090 7091 7092 7093 7094 7412 7414 7416 7434 7435 7436 8102 DIN 439 6923 912 551 982 6924 980 6925 7985 965 966 7981 7982 7983 11024 125 125 126 433 9021 440 6914 6915 6916 553 417 438 6921 ISO DIN 6914 7412 6915 7414 6916 7416 6921 8102 6923 4161 6924 7040 6925 7042 7343 8750 7343 8751 7344 8748 7346 13337 7971 1481 7972 1482 7973 1483 7976 1479 7977 8737 7978 8736 7979 8733 7979 8735 7981 7049 7982 7050 7983 7051 7985 7045 7991 10642 9021 7093 11024 7072 8673 934 8673 971 8674 971-2 8676 961 8677 603 8733 7979 8734 6325 8735 7979 8736 7978 8737 7977 8738 1440 8740 1473 8741 1474 8742 1475 8744 1471 8745 1472 8746 1476 8747 1477 8748 7344 13337 7346 8750 7343 8751 7343 8752 1481 8765 960 10642 7991 10511 985 10512 982 10513 980 971-1 8673 971-2 8674 980 980 982 982 985 1440 1444 1471 1472 1473 1474 1475 1476 1477 1481 6325 7042 10513 7040 10512 10511 8738 2341 8744 8745 8740 8741 8742 8746 8747 8752 8734 1767 10 . completely identical to ISO 4017 M16 x 50-8. all other screw dimensions are already perfectly identical to ISO. For this reason alone the use of nuts in accordance with ISO standards is highly recommended.One of the most significant product changes on the harmonisation of the codes was without doubt the change of the width across flats of all hexagonal products. Part 3: Bolts. studs and nuts (ISO 8839: 1986) Nothing noteworthy 10 1768 . screws and studs for general requirements (ISO 6157-1: 1988) Changes Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Fasteners -.3 DIN-ISO changes to widths across flats Hexagonal widths across flats M10 M12 M14 M22 DIN 17 mm 19 mm 22 mm 32 mm ISO 16 mm 18 mm 21 mm 34 mm 3.4. general changes. nonferrous metal bolts. screws. part 6.1 Technical terms of delivery and basic standards DIN (old) 267 Part 20 267 Part 21 DIN ISO 225 DIN ISO 273 DIN ISO 898 Part 1 267 Part 4 DIN ISO 898 Part 6 267 Part 19 267 Part 19 DIN ISO 7721 267 Part 9 267 Part 1 267 Part 5 267 Part 11 267 Part 12 267 Part 18 ISO – – 225 273 898-1 898-2 898-6 6157-1 6157-3 7721 – – – – – 8839 DIN (new) or DIN EN DIN EN ISO 6157-2 DIN EN ISO 10484 DIN EN 20225 DIN EN 20273 DIN EN ISO 898 Part 1 DIN EN 20898-2 DIN EN ISO 898 Part 6 DIN EN 26157 Part 1 DIN EN 26157 Part 3 DIN EN 27721 DIN ISO 4042 DIN ISO 8992 DIN EN ISO 3269 DIN EN ISO 3506. nuts Widening test on nuts Fasteners. properties of fasteners. screws and studs for special requirements (ISO 6157-3: 1988) Countersunk head screws -. bolts. properties of fasteners. Part 1.Surface discontinuities -. screws. surface discontinuities.Electroplated coatings Fasteners -. fine thread (ISO 898-6: 1988) Fasteners -.Surface discontinuities -. symbols and designations of dimensioning (ISO 225:1991) Mech. 3 DIN EN ISO 2702 DIN EN 28839 Title Fasteners. part 2.Head configuration Nothing noteworthy and gauging (ISO 7721: 1983) Fasteners -. nuts with specified proof load values.Part 1: Bolts. Currently valid standards collections 3. clearance holes for bolts and screws (ISO 273: 1991) Mech. fasteners.4 Standard changeover DIN/ISO. nuts with specified proof load (ISO 898-2: 1992) Mech. properties of fasteners made of carbon steel and alloy steel (ISO 898-1: 1988) Mech. studs and nuts Fasteners – acceptance inspection Mechanical properties of corrosion-resistant steel fasteners – technical terms of delivery Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Heat-treated steel tapping screws – mechanical Nothing noteworthy properties Mechanical properties of fasteners.General requirements for bolts. studs and nuts. 2. screws. classified in accordance with special fields.3. Half-length reverse-taper grooved (ISO 8741:1997) Grooved pins .2 Small metric screws DIN (old) 84 85 963 964 965 965 966 7985 ISO 1207 1580 2009 2010 7046-1 7046-2 7047 7045 DIN (new) or DIN EN DIN EN 21207 DIN EN 21580 DIN EN 22009 DIN EN 22010 DIN EN 27046-1 DIN EN 27046-2 DIN EN 27047 DIN EN 27045 Title Slotted cheese head screws -. shape A Countersunk oval head screws with slot. full length parallel grooved pins with pilot (ISO 8739:1997) Grooved pins -. round stainless steel (ISO 2338:1986) ends Plain washers for clevis pins -. strength class 4. of unhardened steel and austenitic Length I incl.Slotted.one-third-length centre grooved (ISO 8742:1997) Grooved pins with round head (ISO 8746:1997) Grooved pins with countersunk head (ISO 8747:1997) Spring-type straight pins -. of hardened steel and martensitic stainless steel (Dowel pins) (ISO 8734:1997) Nothing noteworthy Increased shearing forces Nothing noteworthy Nothing noteworthy Bevel angle cancelled Shape A/B cancelled 1769 10 . product grade A Head height and diameter in places 3.3 Pins and screws DIN (old) 1 7 1440 1443 1444 1470 1471 1472 1473 1474 1475 1476 1477 1481 6325 ISO 2339 2338 8738 2340 2341 8739 8744 8745 8740 8741 8742 8746 8747 8752 8734 DIN (new) or DIN EN DIN EN 22339 DIN EN 22338 DIN EN 28738 DIN EN 22340 DIN EN 22341 DIN EN 8739 DIN EN 8744 DIN EN 8745 DIN EN 8740 DIN EN 8741 DIN EN 8742 DIN EN 8746 DIN EN 8747 DIN EN 8752 DIN EN 8734 Title Taper pins. product grade A Countersunk screws with slot.Product grade A (ISO 8738: 1986) Clevis pins without head (ISO 2340:1986) Clevis pins with head (ISO 2341:1986) Grooved pins. heavy duty (ISO 8752:1997) Parallel pins.product grade A (ISO 1207: 1992) Flat-headed screws with slot. unhardened (ISO 2339:1986) Changes Length I incl.3.8 Changes Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Countersunk oval head screws with cross recess Head height and (common head): product grade A diameter in places Flat-headed screws with cross recess.Full-length taper grooved (ISO 8744:1997) Grooved pins -.Half length taper grooved (ISO 8745:1997) Outer diameter in places Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy Gooved pins -.4.4. with Nothing noteworthy chamfer (ISO 8740:1997) Grooved pins -.8 Countersunk screws with cross recess (common head): product grade A. round ends Parallel pins.Full-length parallel grooved. strength class 4. shape A Countersunk screws with cross recess (common head): product class A. 9.4. thread to head Changes 4 widths across flats 4 widths across flats Nut height and 4 widths across flats 4 widths across flats 4 widths across flats 4 widths across flats 4 widths across flats Nut height and 4 widths across flats Nut height and 4 widths across flats 4 widths across flats 4 widths across flats 10 1770 . unhardened (ISO 8737:1986) Tapered pins with internal thread. style 1 Hexagon nuts. with metric fine pitch thread Hexagon head bolts with shaft and metric fine pitch thread Hexagon head screws 10. DIN 555 Hexagon head bolt with shank Hexagon head screw Hexagonal nuts.DIN (old) 7977 7978 7979 7979 ISO 8737 8736 8733 8735 DIN (new) or DIN EN DIN EN 28737 DIN EN 28736 DIN EN 8733 DIN EN 8735 Title Tapered pins with external thread. of unhardened steel and austenitic stainless steel (ISO 8733:1997) Parallel pins with internal thread. unhardened (ISO 8736:1986) Parallel pins with internal thread. unchamfered (ISO 4036: 1979) Hexagon thin nuts. of hardened steel and martensitic stainless steel (ISO 8735:1997) Changes Nothing noteworthy Nothing noteworthy Nothing noteworthy Nothing noteworthy 3. product grade C Hexagon head screws. product grade C Hexagon head bolts. style 1.5 Hexagon head screws and nuts DIN (old) 439 T1 439 T2 555 558 601 931 933 934 ISO type 1 934 ISO type 1 960 961 ISO 4036 4035 4034 4018 4016 4014 4017 4032 8673 8765 8676 DIN (new) or DIN EN DIN EN 24036 DIN EN 24035 DIN EN 24034 DIN EN 24018 DIN EN 24016 DIN EN 24014 DIN EN 24017 DIN EN 24032 DIN EN 28673 DIN EN 28765 DIN EN 28676 Title Hexagon thin nuts. unchamfered (ISO 4035: 1986) Hexagon nuts.4 Tapping screws DIN (old) 7971 7972 7973 7976 7981 7982 7983 ISO 1481 1482 1483 1479 7049 7050 7051 DIN (new) or DIN EN DIN ISO 1481 DIN ISO 1482 DIN ISO 1483 DIN ISO 1479 DIN ISO 7049 DIN ISO 7050 DIN ISO 7051 Title Slotted pan head tapping screws (ISO 1481: 1983) Slotted countersunk (flat) head tapping screws (common head style) Slotted raised countersunk (oval) head tapping screws (common head style) Hexagon head tapping screws Cross recessed pan head tapping screws Changes Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height in places Head height and diameter in places Cross recessed countersunk (flat) head tapping Head height and screws (common head style diameter in places Cross recessed raised countersunk (oval) head tapping screws Head height and diameter in places 3. product grade C.4. 4–4.2–22.6 – 5.7–22 22.5 6.1–15.2 1.55–0.3 22.4 2.35–1.44–6.3 1.4 M1.2 20.5) M4 M5 M6 (M7) M8 M10 M12 (M14) M16 (M18) M20 (M22) M24 (M27) M30 Width across flat s DIN 2.6–24.7–24 ISO 4032 (RG) 8673 (FG) ISO type 1 – – – 1.55–2.5 Dimensional changes to hexagonal screws and nuts Nominal size d Sizes to be avoided M1 M1.7–4 4.75–1 0.7–19 20.3–13 14.05–1.05 20.1–16.9 14.95–1.55–0.4–12.25 7.9–18 17.9–3.6 1.9–19 18.9 17.25–10.04–8.6–6.4–4.1–13.75 9.5–23.5 7.1 – 15.9–3.14–6.8 0.3.1–12.4.9–5.1–16.9 8–9.95–25.4–5.2–21.5 22.95–23.5 10.1 – 6.8 15.3–26.2 4 5 5.5 M3 (M3.95–20.75–7. DIN 555 – – – – – – – – – 3.7 4.05 ISO 4034 ISO type 1 0.9 16.75–2 2.8 14.7 24.1–15.2 3.3–11 12.4 10.64–10 10.9–16 16.4 DIN 934 0.6 Threaded pins DIN (old) 417 438 551 553 913 914 915 916 ISO 7435 7436 4766 7434 4026 4027 4028 4029 DIN (new) or DIN EN DIN EN 27435 DIN EN 27436 DIN EN 24766 DIN EN 27434 DIN 913 DIN 914 DIN 915 DIN 916 Title Slotted set screws with long dog point (ISO 7431: 1983) Slotted set screws with cup point (ISO 7436: 1983) Slotted set screws with flat point (ISO 4766: 1983) Slotted set screws with cone point (ISO 7431: 1983) Socket set screws with flat point Slotted set screws with cone point Slotted set screws with dog point Slotted set screws with cup point Changes Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places Head height and diameter in places 3.1–19.1–14.3–25.35–1.37–10.9 17.9–5.6 1771 10 .75–2 2.4–7.3 1.1–13.3–15 14.5 6 7 8 10 11 13 17 19 22 24 27 30 32 36 41 46 34 16 18 21 – ISO – – – Nut height m min.2 4.05–1.8 16.2–5.2 M1.7–5 5.2 – 6.05 22.4 20.8 2.1–18.64–8 9.15–2.25–8.6 1.8 8.4 2. – max.9–18 18.6 4.2 12.6 M2 M2.8 2.8 24.15–2.5 3 3 3.9 15.55–2.1–20.8 12.8 – – – – – – – – 4.6 4.75 – 12. 4–34 34.4–45.75–46.4–36 36.12 ~0.8 C (average) 7H 27.4–38.4–38 40.5 29.9 36.9 34.25 40. Product class Thread tolerance Strength class Steel Core range ~M5-39 >M39 Mechanical properties according to standard ST – standard thread.9 31.9 46.83–1.4–29.4–48 49.25 46.4–34 34.8.4–45 46.9 49. 24.4–52.Nominal size d (M33) M36 (M39) M42 (M45) M48 (M52) M56 (M60) M64 >M64 Width across flat s 50 55 60 65 70 75 80 85 90 95 – ≤ M4 M5–M39 ≥ M42 Nut height m min.4–31.7 29. – max.4–28.75–35.3 32.4–45 46.9 43.7–26 27.8–33.84–0.4–42 43.1–51 –/– 0.5–52.4–31 32.8 ≤ M16 = A (average) >M16 = B (average roughness) 6H 6.05 29.4–31 31.4–38 40.25 34.5 Following agreement DIN 267 Part 4 ISO 898 Part 2 (ST) d ≤ M39 10 1772 .95–27.4 32.4–48 49.75–37.10 (ISO 8673 = strength class 10 ≤ M16) Following agreement DIN 267 Part 4 ISO 898 Part 2 (ST) Part 6 (FT) Nut height factor m/d approx.4 – – 0.75–49.8–34.25 43.95–30.75–39.4–36.25 36. FT – fine thread 5 M16 < d ≤ M39 = 4.8 0.8 24.8 27.4–34.25 32.4–48.4–36 36.93 0.1–51 to M100*6 0.05 27.75–43.25 49.75–32.4–42 43.4–29 29.4–42.5 to M100*6 – 0.9 40. MANUFACTURING SCREWS AND NUTS 4. cold extrusion and reducing. This procedure is usually used for large quantities. The following diagram is intended to make the production processes clearer: (wire). machining. by pressure forging. Screw manufacturers usually receive the wire coiled on rolls that often weigh over 1000 kg.1 Cold forming (cold extrusion) In modern fastening technology the majority of fasteners are made using the cold forming procedure. With the materials differences are made. The term solid or cold forming was coined for this type of production. or a combination of these procedures. Diagram of the stages for a hexagon head screw Fig. the following manufacturing processes are differentiated: On the one hand there is forming without cutting and on the other. between unalloyed and alloyed steels. The choice of the suitable forming machine depends on the size of the fastener and on the degree of forming.4. A decisive role for the quality of the final product is played by the choice and the quality of the input material Wire Descaling Intermediate section upsetting Finishing Calibrating Round die thread rolling Nuts are usually produced with the cold or hot forming procedure as well. For example. The designer of a screw or a fastener tries during development to harmonise the advantages and disadvantages of the different materials with the requirements specified for the fastener. The choice of one or the other procedure depends on the one hand on the size and on the other on the required quantities. it is the most rational method. The greater the degree of forming. N: O verview of the various production processes 4. The wire is normally phosphate treated to enable the wire to be worked perfectly and to minimise tool wear. 1773 10 .1 Manufacturing processes In principle. if increased strengths are required.1. usually in multistage processes. In this procedure. the more forming stages are required. Sharp-edged transitions or thin profiles are unfavourable for cold forming and lead to increased tool wear. along with corrosion-resistant steels. from an economic aspect. because. it is absolutely essential to subject the parts after pressing to a heat treatment process in order to be able to influence the mechanical properties specifically. With forming without cutting there is a further differentiation between cold and hot forming. the fastener is formed. The diameter of the input material depends on the largest diameter of the component.2 Thread production Where screws are mass-produced.7 can be achieved with this production procedure without any problems.1. bars with a length of up to 6 m are used. In contrast to cold or hot forming. In the case of large production runs the blanks are often produced with the cold extrusion method and are then machined. the screw is rolled between two rolling dies (flat dies). milling. This heating up enables even complicated geometries or very high degrees of forming to be realised. but this has lost a great deal of importance because of the technical possibilities of cold pressing. and longer pieces starting from approx. M27. Advantages of cold forming: • Optimal use of material • Very high output • High dimensional accuracy and surface quality • Increase of strength properties through strain hardening • Run of the chamfers in press parts in accordance with the load 4. A typical feature for a hot-formed component is the raw surface structure. Usually. parts are possible that cannot be produced using cold forming because of the very small volumes. one of which is fixed and the other running.3 Machining Machining is usually understood as processing steps such as turning. In this procedure.1. the input material (usually bars) is heated wholly or partially to forging temperature. 4. 10 1774 . the required contour of the component is cut from the input material using a turning tool.2 Hot forming This production method is used mainly to manufacture large diameters starting with approx. and this creates the thread (see the diagram). the chamfer course of the input material is destroyed. This production procedure is used either if the production run is not very large or if the part geometry cannot be complied with in cold or hot forming procedures because of sharp edges.4 or Rz 1. The thread is usually applied before hardening and tempering. With this type of thread production it is possible to fit several hundred screws per minute with a thread. If special requirements mean that the thread is applied after the heat treatment process. In addition.Diagram of the stages for a hexagonal nut During turning. the thread is usually formed or rolled. Strain hardening is not carried out during hot forming! Advantages of hot forming: • Enables production of complicated geometries • Low production runs • Large diameters and lengths 4. With this procedure. Surface roughnesses of Ra 0. 300 mm. small radiuses or even nominal sizes. The most common method with regard to fasteners is turning. grinding or reaming. the thread is referred to as “finally rolled”. or because of a very high degree of forming. Fixed die External diameter of the thread Thread cutting on an automatic lathe with a taper tap Running die 4.2.1 Fibre pattern The two diagrams show very clearly the differences between a rolled and a cut thread. With thread forming the material is work hardened again in addition, and the fibre pattern is not interrupted. In this case, the original diameter of the screw is approximately the same as the flank diameter. With thread cutting, the original diameter of the screw is the same as the nominal diameter of the thread. The fibre pattern is interrupted by the cutting. Chamfer course on thread cutting Chamfer course on thread forming Other methods for making threads: Plunge cutting Tool rolls that are driven at the same speed rotate in the same direction. The workpiece rotates without being axially displaced. This method can be used to make threads with very high pitch accuracy. Continuous method The thread pitch is generated by inclining the roller axes by the pitch angle. The workpiece is given an axial thrust and moves by one thread pitch in an axial direction, with a full rotation. Overlength threads can be made in this way. Thread cutting In this procedure the thread is made by means of a tap or a screw stock. With screws, this procedure is mainly used for very low production runs or with machined parts as well. However, things are different when a female thread is made. In this case the thread is usually cut with a screw tap or taper tap. 4.3 Heat treatment 4.3.1 Hardening and tempering The combination “hardening” and subsequent “ tempering” is referred to as hardening and tempering. DIN EN ISO 898 Part 1 prescribes hardening and tempering for screws from strength class 8.8, and DIN EN 20898 Part 2 prescribes it for nuts in strength class 05 and 8 (>M16), and from strength class 10. 4.3.2 Hardening The screw is heated to a specific temperature among other things in dependence on its carbon content and kept at this temperature for a long period. This changes the microstructure. A great increase in hardness is achieved through the subsequent quenching (water, oil, etc.). 1775 10 4.3.3 Annealing The glass-hard and therefore brittle material cannot be used in practice in this condition. The material must be heated up again to a minimum temperature specified in the standard, in order to reduce the distortions in the microstructure. It is true that this measure reduces the hardness that was reached beforehand (but this is much higher than the values of the untreated material), but greater ductility is achieved. This procedure is an important aid for manufacturers to make screws that satisfy the requirements demanded by users. 4.3.4 Case hardening This procedure is used among other things for tapping screws, thread grooving and self-drilling screws. In this case, very hard surfaces are decisive, so that these screws are able to make their own thread automatically. The screw core, in contrast, is soft. Steels with a carbon content of 0.05% to 0.2% are used for these types of screws. The steels are heated and kept for a long time in an atmosphere that gives off carbon (e.g. methane). The carbon diffuses into the surface zones and in this way increases the local carbon content. This process is known as carburisation. Finally, the material is quenched and in this way hardened in the surface zones. This has the advantage that the surface is very hard, but sufficient ductility remains in the core of the screw. 4.3.5 Stress relief annealing There are a number of different annealing procedures which have different effects in each case on the microstructure and the states of stresses in the material. One very important procedure in the context of fasteners is stress relief annealing (heating to approx. 600°C and maintaining this temperature for a long period). The strain hardening created on cold forming can be reversed by stress relief annealing. This is particularly important for screws in strength classes 4.6 and 5.6, because here there has to be a large elongation of the screw. 4.3.6 Tempering Tempering is the thermal treatment of high strength components (strengths ≥1000 MPa or hardnesses ≥320 HV) with the aim of minimising the risk of hydrogen embrittlement. Tempering must be carried out at the latest 4 hours after the conclusion of the galvanic surface treatment. The minimum temperature depends on the strength classes or on the materials that are used. 10 1776 5. SURFACE PROTECTION 5.1 Corrosion About 4% of the gross national product of a western industrial nation is destroyed by corrosion. About 25% of this could be avoided by applying existing knowledge. Corrosion is the reaction of a metallic material with its environment that causes a measurable change to the material and may lead to an impairment of the function of a component or of a complete system. This reaction is usually of an electrochemical nature, but in some cases it may also be of a chemical or metal-physical nature. We can also observe corrosion in our daily lives: • Rust on vehicles, railings and fences • Creeping destruction of road structures, bridges, buildings • Leaks in water pipelines and heating pipes made of steel Crevice corrosion Corrosion is unavoidable – but the damage caused by corrosion can be avoided through the correct planning of suitable corrosion protection measures. The corrosion system of a screw assembly should, under operating conditions, be at least as corrosion-resistant as the parts that are to be connected. The design engineer’s job is to decide on the necessary corrosion protection measures. Here, the wear reserve of a corrosion protection system and the ambient conditions have to be taken into account. The ways in which corrosion manifests itself can vary greatly. (See DIN 50900 for corrosion types). 5.2 Corrosion types Surface corrosion e.g. rust Electrolyte – Contact corrosion + 1777 10 Corrosion rates, reference values in μm per year Medium Country air Urban air Industrial air Sea air Zincnon-chromated 1–3 ≤6 6–20 2–15 Brass Ms 63 ≤4 ≤4 ≤8 ≤6 Copper CuNi 1.5 Si ≤2 ≤2 ≤4 ≤3 Unalloyed steel unprotected ≤ 80 ≤ 270 ≤ 170 ≤ 170 Tab. 1 5.3 Frequently used types of coatings for fasteners 5.3.1 Non-metallic coatings Designation Rubbing with oil Burnishing Procedure Workpieces are immersed in oil Application Bright steel parts Suitable for short-term corrosion protection e.g. during transport Corrosion resistance Undefined Workpieces are immersed in acid Parts of weapons Salt spray test approx. 0.5 h or alkaline solutions. Gauges and measuring technology Corrosion protection oil can Oxide layers with a (brown) black increase resistance colour are created through reaction No layer development Purpose: formation of a weak protective layer on the surface No hydrogen embrittlement Steel component in metal phosphate bath or chamber with metal phosphate solution 5–15 µm layer connected with the material Iron/manganese/nickel/zinc phosphate Salt spray test: approx. 3 h Cold forming of steel Combination with corrosion Corrosion protection oil can increase resistance protection media Reduction of wear on manganese phosphatising Primer for coat of lacquer (prevents rust creep) Phosphatising Tab. 2 5.3.2 Metallic coatings Designation Electro-galvanised Procedure Metal deposition in the galvanic bath After treatment through passivation Optionally with sealing Metal deposition in the galvanic bath After treatment through passivation Optionally with sealing Application In areas with low to average corrosion exposure, e.g. general mechanical engineering, electrical engineering – system-dependent thermal loadability 80°C–120°C In areas with extreme corrosion exposure – e.g. components in the engine compartment – or on brakes, where normal electro plating is unable to cope not only because of the great heat but also because of the effect of salt in winter Corrosion resistance Corrosion resistance to 120 h against backing metal corrosion (red rust) in the salt spray test in accordance with DIN 50021 SS (ISO 9227) (layer thicknesses and dependent on the system) Greatest cathodic corrosion protection – even with layer thicknesses from 5 μm (important for fits) No voluminous corrosion products with zinc-nickel) Corrosion resistance to 720 h to backing metal corrosion (red rust) in the salt spray test in accordance with DIN 50021 SS (ISO 9227) (layer thicknesses and systemdependent) Because of its electrochemical properties with regard to steel nickel cannot take over the function of a reactive anode. Galvanic zinc alloy layer (zinc-iron) (zinc-nickel) Electro-nickel plated Metal deposition in the galvanic bath Optionally with impregnation 10 In areas with very low corrosion exposure, e.g. decorative applications in interiors Component of a multilayer system e.g. copper-nickel-chromium 1778 Designation Electro-chrome plated Procedure Metal deposition in the galvanic bath Usually as a coating on a nickelplated surface Thickness of the chromium layer usually between 0.2 µm and 0.5 µm Metal powder is hammered onto the components, glass beads are used as “impact material”. Coating is carried out by means of a chemical medium, electricity is not used. Coating is carried out at room temperature. Immersion in molten metal bath Min. layer thicknesses approx. 40 µm Process temperature approx. 450°C Greater corrosion protection Not suitable for small screws Cathodic corrosion protection Application In areas with very low corrosion exposure, e.g. decorative applications in interiors Component of a multilayer system e.g. copper-nickel-chromium Retaining washers, high-strength spring-mounted components (no risk of hydrogen induction during the coating process) Corrosion resistance Because of its electrochemical properties with regard to steel chromium cannot take over the function of a reactive anode. Mechanically galvanised Corrosion resistance to 144 h against backing metal corrosion (red rust) in the salt spray test in accordance with DIN 50021 SS (ISO 9227) (layer thicknesses and system-dependent) Corrosion resistance between 5 and 25 years depending on the environmental conditions Hot-dip galvanising Fasteners for steel construction. For example, HV kits. Applicable for fasteners ≥ M12 Tab. 3 5.3.3 Other coatings Procedure Veralising Brass coating Copperplating Silver-plating Tinning Anodising Ruspert Explanations Special hard nickel-plating. Brass coatings are used mainly for decorative purposes. Apart from this, steel parts are coated with brass to improve the adherence of rubber on steel. If necessary, as an intermediate layer before nickel-plating, chrome-plating and silverplating. As a cover layer for decorative purposes. Silver coatings are used for decorative and technical purposes. Tinning is used mainly to achieve or improve soldering capability (soft solder). Serves at the same time as corrosion protection. Thermal after-treatment not possible. A protective layer is generated in aluminium through anodic oxidation that works as corrosion protection and prevents staining. Nearly all colour shades can be achieved for decorative purposes. High-grade zinc-aluminium flake coating, can be produced in extremely different colours. Depending on the layer thickness 500 h or 1000 h in fog test (DIN 50021). Maximum application temperature Burnishing (blackening) Chemical procedure. Bath temperature approx. 140°C with subsequent oiling. For decorative purposes. Only slight corrosion protection. Blackening (stainless) Polyseal Chemical procedure. The corrosion resistance of A1–A5 can be impaired by this. For decorative purposes. Not suitable for external application. Following a conventional immersion procedure a zinc-phosphate layer is applied at first. An organic protective layer is then applied that is precipitation-hardened at approx. 200°C. Following this, a rust-protection oil is applied as well. This protective coating can be carried out in different colours (layer thickness approx. 12 µm). With nickel-plated parts above all, the micropores can be sealed with wax through after-treatment in dewatering fluid with added wax. Significant improvement of corrosion resistance. The wax film is dry, invisible. 70 °C Impregnating Tab. 4 1779 10 It stipulates layer thicknesses and provides recommendations for reducing the risk of hydrogen embrittlement in high-strength or very hard fasteners.5.4. DIN EN ISO 4042 does not differentiate between surface coatings containing chromium (VI) and those without chromium (VI). 6: Extract from ISO 4042 Table C Passivation/chromating Gloss level Matte Passivation through Code letter chromating No colour Yellowish shimmering to yellow-brown iridescent Olive green to olive brown Bright No colour Yellowish shimmering to yellow-brown iridescent Olive green to olive brown Glossy No colour Yellowish shimmering to yellow-brown iridescent Olive green to olive brown A C D E G H J L M Bluish to bluish iridescent B Table A Coating metal/alloy Coating metal/alloy Abbreviation Zn Cd Cu CuZn Ni b Ni b Cr r CuNi b CuNi b Cr r Sn Element Zinc Cadmium Copper Copper-zinc Nickel Nickel-chromium Copper-nickel Copper-nickelchromium Tin Copper-tin A B C D E F G H J K Code letter Bluish to bluish iridescent F Bluish to bluish iridescent K 10 CuSn 1780 . Designation example Coating metal/alloy Abbreviation Ag CuAg ZnNi ZnCo ZnFe Element Silver Copper-silver Zinc-nickel Zinc-cobalt Zinc-iron Code letter L N P O R Tab. In the first place. this standard stipulates the dimensional requirements for fasteners made of steel and copper alloys that are to be given a galvanic coating. or with surfacehardened fasteners.1 Designation system in accordance with DIN EN ISO 4042 The most common system for the abbreviated designation of galvanic surfaces on fasteners is the standard DIN EN ISO 4042.4 Standardisation of galvanic corrosion protection systems 5. 5: Extract from ISO 4042 Table B layer thickness Layer thickness in µm One coating metal No layer thickness prescribed 3 5 8 10 12 15 20 25 30 Two coating metals – – 2+3 3+5 4+6 4+8 5+10 8+12 10+15 12+18 0 1 2 3 9 4 5 6 7 8 Code no A surface designation must always consist of the code letter table A + code number table B + code letter table C X Coating metal Minimum thickness After-treatment X X Tab. The main purpose of the coatings or coating systems is the corrosion protection of components made of ferrous materials. A3H. A2G. A1F. zinc/iron) as the alloy components. A3E. A2T Nominal White rust layer h thickness 3 5 8 3 5 8 3 5 8 3 5 8 3 5 8 2 6 6 6 12 24 24 48 72 24 72 96 12 12 24 Red rust h 12 24 48 12 36 72 24 72 120 24 96 144 36 72 96 Tab. This standard defines the designations for the coating systems that are shown below and stipulates minimum corrosion resistances in the described test procedures as well as the minimum layer thicknesses required for this.4. A3J B Blue iridescent A1B. A2F. 8 5. A3K C Yellow iridescent A1C. A1S. 7: Extract from ISO 4042 5. A3L D Olive green A1D. A1J A2A. A1H. A1K A2B. A3M BK Sooty to black A1R. A2E. A2M A3D. A1G. The zinc alloy coatings contain nickel or iron (zinc/ nickel.Gloss level High gloss Any Matte Bright Glossy Passivation through Code letter chromating No colour As B.3 Designation system in accordance with DIN 50979 This standard applies to electroplated and Cr(VI)-free passivated zinc and zinc alloy coatings on ferrous materi als. A2H. C or D Brown-Black to black Brown-Black to black Brown-Black to black N P R S T U All gloss levels Without chromating Tab. 1781 10 . A1T A2R. A2L A3C. A3G. A1M A2D. A2K A3B. A3F. A2S. A1E.4. A2J A3A.2 Reference values for corrosion resistances in the salt spray test DIN 50021 SS (ISO 9227) Procedure group Passivation colourless Passivation blue Chromating yellow Chromating olive Chromating black Chromating designation A Inherent colour of the chromate layer Transparent Designation in accordance with ISO 4042 A1A. A1L A2C. The influence of sealings on the functional properties of the component. is to be assessed on the basis of the component. compatibility with fuels. Products that can be removed with cold cleaners.4.4. 9: Extract from DIN 50979 5. In case of the special requirements for the surface functionality the use of the sealing and the type of sealant have to be agreed. on an oil.4. Sealings consist of Cr(VI)-free organic and/or inorganic compounds. such as. grease. Passivation or procedure group Transparent passivated Iridescent passivated Black passivated Abbreviation Appearance of the surface An Cn Fn Colourless to coloured. because the band width of the possible surface modifications through sealings is large.g. 10: Extract from DIN 50979 5. Abbreviation T0 T2 Description Without sealing With sealing Tab.5.5 Passivation Passivating means making conversion layers by treating with suitable Cr(VI) free solutions in order to improve the corrosion resistance of the coatings. for example. are not considered as sealings in the context of this standard. transition resistance.4 Designation of the galvanic coatings The galvanic coatings consist of zinc or zinc alloys Abbreviation Definition Zn ZnFe ZnNi Zinc coating without added alloy partner Zinc alloy coating with a mass share of 0. In most cases the sealings also eliminate the interference colours (iridescences) formed by passivating.0% iron Zinc alloy coating with a mass share of 12% to 16% nickel Tab.6 Sealings Sealings increase corrosion resistance and usually have a layer thickness up to 2 μm. 11: Extract from DIN 50979 10 1782 . weldability. iridescent Coloured iridescent Black Notes Frequently referred to as thin layer passivation Frequently referred to as thick layer passivation Tab. glued joints. e. Colouring is possible. wax basis.3% to 1. threads that are not true to gauge size and unusable internal drives must be reckoned with. The coating is then burnt in a continuous furnace at 150°C–300°C (depends on the system). a thinnest local layer thickness of 5 μm (5) and black passivated (Fn). iridescent passivated Galv. black passivated Zn//An//T0 Zn//Cn//T0 Zn//Cn//T2 ZnFe//Cn//T0 ZnFe//Cn//T2 ZnNi//Cn//T0 ZnNi//Cn//T2 ZnFe//Fn//T2 ZnNi//Fn//T2 ZnNi//Fn//T0 Drum Frame Drum Frame Drum Frame Drum Frame Drum Frame Drum Frame Drum Frame Drum Frame Drum Frame Drum Frame 8 16 72 120 120 168 96 168 144 216 120 192 168 360 120 168 168 240 48 72 48 72 144 192 192 264 168 240 216 312 480 600 600 720 192 264 480 600 480 600 8 µm 72 96 216 264 264 360 240 312 288 408 720 720 720 720 264 360 720 720 720 720 12 µm 96 120 288 336 360 480 312 384 384 528 720 720 720 720 360 480 720 720 720 720 Tab. iridescent passivated and sealed Galv. a thinnest local layer thickness of 8 μm (8) and iridescent passivated (Cn). Part of the coating substance is thrown off through centrifugation. This procedure is unsuitable for threaded parts ≤M6 and for fasteners with small internal drives or fine contours. In this way a largely even layer is created. iridescent passivated Galv.4.5 Standardisation of non-electrolytically applied corrosion protection systems 5. Here. transparent passivated Galv. zinc coating. iridescent passivated and sealed Galv. iridescent passivated and sealed Galv. zinc coating. zinc iron alloy coating.5. zinc nickel alloy coating. zinc coating. without sealing (T0) Fe// ZnNi8//Cn//T0 Zinc/iron alloy coating on a component made of steel (Fe). zinc nickel alloy coating.5. iridescent passivated Galv. zinc iron alloy coating. If suitable cleaning procedures are used hydrogen inducement in the coating process is ruled out. To obtain an even and covering layer it is necessary that the parts to be coated pass through two coating passes. Larger parts can also be coated by spraying the coating medium on.1 Zinc flake systems The parts that are to be coated are placed in a centrifuge basket and immersed in the coating medium. 12: Extract from DIN 50979 Designation examples: Zinc/nickel alloy coating on a component made of steel (Fe). 1783 10 . black passivated and sealed Galv. zinc nickel alloy coating.7 Minimum layer thicknesses and test duration Type of surface protective layer Execution type Procedure type Without coating corrosion Minimum test duration in h Without base material corrosion (in dependence on the Zn or Zn alloy layer thickness) 5 µm Galv. zinc iron alloy coating. with sealing (T2) Fe//ZnFe5//Fn//T2 5. zinc nickel alloy coating. black passivated and sealed Galv. Zinc flake systems are suitable for coating high-strength components. in other cases the abbreviation flZn applies. are required. DIN EN ISO 10684 provides information for pretreatment and galvanising processes that minimise the risk of brittle fractures.g.2 Standardisation of non-electrolytically applied corrosion protection systems Designations in accordance with DIN EN ISO 10683 • flZn-480h = zinc flake coating (flZn).5. Dacromet 500A. Dacromet 320A 5. Only normal temperature galvanising should be applied above the thread size M24. e. Delta Tone/Seal • flZnyc-480h = zinc flake coating (flZn). corrosion resistance to RR 480 hours. (GAV) and of the Deutscher Schraubenverband e. e. Hot dip galvanising is permissible to strength class 10. the fasteners are usually cooled down in a water bath. it can be converted as follows into the layer thickness: • Coating with chromate: 4. with integrated lubricant. e. Dacromet 320A.V. Dacromet 500A.g.5 g/m2 corresponds to a thickness of 1 μm • Coating without chromate: 3. Dacromet 320A+VL • flZnnc-480h = zinc flake coating (flZn). Delta Protect. Geomet 321A+VL.6 Standardisation of the hot-dip galvanising of screws in accordance with DIN EN ISO 10684 5. Geomet 321A. corrosion resistance to RR 480 hours. corrosion resistance to RR 480 hours.g. Dacromet 500A • flZn-480h-L = zinc flake coating (flZn). with chromate. 13: Extract from DIN EN ISO 10683 10 1784 .1 Procedure and area of application Hot dip galvanising is a procedure in which the fasteners are immersed in a molten bath after suitable pre-treatment.9. Further specifications.8 g/m2 corresponds to a thickness of 1 μm The buyer may specify whether he wants to have a coating with chromate (flZnyc) or without chromate (flZnnc). Geomet 500A. e. with subsequently applied lubricant. Tab. which are described in the technical guidelines of the Gemeinschaftsausschusses Verzinken e. Geomet 500A.9. Excessive zinc is then thrown off in a centrifuge in order to set the zinc layer thickness required for corrosion protection.g. corrosion resistance to RR 480 hours. (DSV).V.6. e. Following this. Delta Tone/Seal • flZnL-480h = zinc flake coating (flZn). corrosion resistance to RR 480 hours. without chromate. Corrosion resistances in accordance with DIN 50021 SS (ISO 9227) in dependence on the layer thickness Minimum values for the local layer thickness (if specified by buyer) Test duration in hours (salt spray test) 240 480 720 960 Coating with chromate (flZnyc) µm 4 5 8 9 Coating without chromate (flZnnc) µm 6 8 10 12 If the layer weight per unit of area in g/m2 is specified by the buyer.5. Geomet 321A. Geomet 500A.g. in particular with screws in strength class 10. with its thickness of at least 50 μm on average.1% by weight of the above-mentioned substances (cadmium 0. hexavalent chromium. the thread is not cut until after galvanising.7 Restriction on the use of hazardous substances 5.35% by weight • Lead as alloy element in aluminium up to 0. These methods may not be mixed. Exceptions (among others) • Lead as alloy element in steel up to 0.01% by weight) per homogeneous material is permissible. polybrominated biphenyl (PBB) or polybrominated diphenyl ethers (PBDE). because the zinc coating.4% by weight • Lead as alloy element in copper alloys up to 4. 14: Tolerance systems on pairing hot-dip galvanised screws and nuts The special marking is to be applied after the strength class marking. Starting from the zero line of the thread tolerance system.2 Thread tolerances and designation system Two different ways of proceeding have proved their worth for creating sufficient space for the quite thick coating when screws and nuts are paired. 5. leads to a reduction of thread overlapping. cadmium. In the building industry this is in fact prescribed in standards. Example: Hexagon head screw ISO 4014 M12x80 .7. The load bearing capacity of the paired threads can be reduced with thread sizes less than M12. the space for the coating is placed either in the screw or in the nut thread. 5.1 RoHS Electrical and electronic equipment brought onto the market from 1 July 2006 may not contain any lead.0% by weight Up to 0.With female thread parts such as nuts. It is therefore very advisable to obtain hot-dip galvanised fasteners in a set.8. Mixing the procedures 1 and 2 shown in table 15 leads either to a reduction of the connection’s load bearing capability or to assembly problems .6. Nut thread tolerance Procedure 1 Special marking Procedure 2 Special marking 6AZ/6AX „Z“ or „X“ 6H/6G None Screw thread tolerance before galvanising 6g/6h None 6az „U“ Tab. the hot-dip galvanising is expressed by the notation “tZn”. In the order designation.8U – tZn 1785 10 . mercury. 5 t gross vehicle weight) Materials and components for vehicles brought onto the market from 1 July 2007 may not contain any lead. mercury.1% by weight of the above-mentioned substances (cadmium 0. This concerns: All vehicles with a gross vehicle weight not exceeding 3.01% by weight) per homogeneous material is permissible. 10 . Exceptions include • Lead as alloy element in steel up to 0. a complete elimination of the risk of brittle fractures cannot be guaranteed under the current state of the art. cadmium or hexavalent chromium. However.2 ELV End-of life vehicles directive (up to 3.5 t 5.g.0% by weight Up to 0.7. Tempering the components immediately after the coating process contributes to minimising the risk.8 Hydrogen embrittlement With galvanically coated steel components with tensile strengths Rm ≥1000 Mpa or hardness ≥320 HV that are subject to tensile stress there is a risk of a hydrogeninduced brittle fracture. alternative coating systems should be preferred.35% by weight • Hexavalent chromium in corrosion protection layers (to 01 July 2007) • Lead as alloy element in copper alloys up to 4. e. Corrosion protection and coating systems should be selected for safety components that exclude the possibility of hydrogen inducement during coating through the procedure. If the risk 1786 of a hydrogen-induced brittle fracture has to be reduced. mechanical galvanising and zinc flake coatings.This concerns: • Large and small household appliances • IT and telecommunications equipment • Consumer equipment • Lighting equipment • Electric and electronic tools. with the exception of large-scale stationary industrial tools • Toys • Sports and leisure equipment • Medical devices • Monitoring and control instruments • Automatic dispensers 5. Users of fasteners are familiar with the respective purposes and the resulting requirements and must select the most suitable surface system themselves. insofar as they are not added intentionally. the preselection of the screw is carried out in the first step in accordance with the following table. provides fundamental information on dimensioning.1 A pproximate calculation of the dimension or the strength classes of screws (in accordance with VDI 2230) On the basis of the above-mentioned findings. starting from the known load ratios.9 8.000 160.000 25.000 M3 M4 M4 M5 M6 M8 M10 M12 M16 M20 M24 M30 M36 10. The calculation of a screw assembly starts from the operating force FB that works on the joint from the outside. It must also be taken into account that. further criteria are then to be checked in accordance with VDI 2230.000 250.000 63. Depending on the application.600 M3 M3 M3 M3 M3 M3 B2 If the design has to use FAmax: 2 steps for dynamic and eccentric axial force or 1787 10 .300 10. a shear force FQ.9 M3 M4 M5 M6 M8 M10 M12 M14 M18 M22 M27 M33 M39 8. that a loss of preload force can occur through setting processes and temperature changes.000 6. depending on the chosen assembly method and on the frictional conditions. 1 A From column 1 choose the next higher force to the one that acts on the joint.000 100. published in 2003.000 16.9 10. If the combined load (lengthwise and shear forces FAmax <FQmax/μTmin) apply.8 M4 M5 M6 M8 M10 M12 M14 M16 M20 M24 M30 M36 Tab. An approximate dimensioning is often sufficient for an initial selection of the suitable screw dimension. 6. it must be taken into account.9 2. 1 Force in N 2 3 4 1 Force in N 2 3 4 Nominal diameter in mm Strength class 12. DIMENSIONING METRIC SCREW ASSEMBLIES VDI guideline 2230. BT he necessary minimum preload force FMmin is found by proceeding as follows from this figure: B1 I f the design has to use FQmax: four steps for static or dynamic shear force FQ FQ Nominal diameter in mm Strength class 12. a bending moment Mb and where applicable a torque MT at the individual screw position.8 250 400 630 1. the assembly preload force FM can disperse in more or less wide limits. in particular of high-strength screw assemblies in engineering. This operating force and the elastic deformations of the components that it causes bring about an axial operating force FA.000 630.6.000 40. only FQmax is to be used.000 1.500 4. When the necessary screw dimension is calculated mathematically.000 400. g. A 10.000 N (= FMmax) D The screw size M12 is now read in column 3 for strength class 10.9. the tightening factor αA has to be selected.000 N is the next higher force in column 1 for the force FA B 2 additional steps because of eccentric and dynamic axial force Reading: 25. the required screw dimension in mm for the appropriate strength class for the screw is found in columns 2 to 4. 6.2 Choosing the tightening method and the mode of procedure Tightening factor αA (taking the tightening uncertainty into account) All tightening methods are more or less accurate. Example: A joint is subjected dynamically and eccentrically to an axial force of 9000 N (FA). FA or 1 step for dynamic and concentric or static and eccentric axial force FA FA FA FA or 0 steps for static and concentric axial force FA FA C The required maximum preload force FMmax is found by proceeding from force FMmin with: 2 steps for tightening the screw with a simple screwdriver which is set for a tightening torque or 10 1788 .000 N (= FMmin) C 1 additional step because of the tightening method using a torque wrench Reading: 40. which is set by means of the dynamic torque measurement or elongation of the screw or 0 steps for tightening by angle control in the plastic range or by computerised yield point control D Next to the number that is found. fast or slow tightening of the screw) Depending on whether the influences referred to above can be controlled. The installation is carried out using a torque wrench.FA 1 step for tightening with a torque wrench or precision screwdriver. The strength class was stipulated previously as strength class 10.9. This is caused by: • the large range of distribution of the friction that actually occurs during installation (friction figures can only be estimated roughly for the calculation) • differences in the manipulation with the torque wrench (e. Higher values for: large angle of rotation.7 to 2.4 ±9% to ±17% The preload force distribution is determined basically through the distribution of the yield point in the installed screw batch. torque signalling wrench or mechanical screw driver with dynamic torque measuring Torque controlled tightening with torque wrench. e.e.2 to 1.2 to 1.g. 1.2 to 1. e. 20). nation of preliminary factor αA is therefore not applicable for these power-operated or torque and angle of tightening methods.5 ±26% to ±43% (coefficient of friction class A) 2.and lubrication ratios) • Lower values for long screws (lK/d≥5) • Higher values for short screws (lK/d≤2) Lower values: large number of setting or control tests necessary (e. relatively resilient connections and fine threads Very hard countersurfaces in combination with rough surface. The distribution depends essentially on the accuracy of the measuring method. Low distribution of the given torque (e.g. i. as well as the coefficients of friction classes in accordance with the following table. greater fault with indirect coupling • The exact determination of the screw's axial elastic flexibility is necessary.6 1. relatively stiff connections relatively low hardness of the countersurface Counter-surfaces that do not tend to “seize”.4 to 1.g.05 to 1. ±5%) necessary.6 to 2.1 to 1.tion of the screws for FMmax with the tightening controlled tightening.4 ±9% to ±17% Yield strength Input of the relative controlled tightening. Lower values for: measuring torque wrench on even tightening and for precision torque wrenches Higher values for: signalling or collapsing torque wrench Lower values for: low angle of rotation. by means of elongation measurements of the screw Determining the target torques by estimating the coefficient of friction (surface. A construcRotation angle Experimental determi. manual rotation (stages) Hydraulic tightening Torque controlled tightening with torque wrench.0 ±23% to ±33% (coefficient of friction class B) 1.g.2 ±2% to ±10% Tightening method Setting method Notes • Calibration values required • With lK/d<2 progressive fault increase to be noted • Smaller fault with direct mechanical coupling. Reference values for the tightening factor αA Tightening factor Distribution αA 1. The screws are dimensioned here for FMmin. torque signalling wrench or mechanical screw driver with dynamic torque measuring Setting by means of length or pressure measuring Experimental determination of target torques at the original screw part. i.5 to 4 ±43% to ±60% Tightening with impact or impulse screw driver Setting the screws by means of the retightening torque. 2 1789 10 . • With lK/d<2 progressive fault increase to be noted Elongation-controlled Sound transmission tightening with time ultrasound 1.5 ±5% to ±20% Mechanical length measuring Setting by means of elongation measurement 1.e.6 ±9% to ±23% ±17% to ±23% 1. torque – angle of power-operated or rotation coefficients manual 1. phosphated or with sufficient lubrication.A calculation is therefore made taking account of the tightening and setting method. which comprises the target tightening torque (for the estimated coefficient of friction) and a supplement Lower values for: • large number of setting tests (retightening torque) • on the horizontal branch of the screw driver characteristics • impulse transmission without play Tab. PA. PA.A different coefficient of friction “μ” has to be selected. coatings such as Zn. PI in solid film lubricants.3 A llocation of friction coefficients with reference values to different materials/surfaces and lubrication conditions in screw assemblies (in accordance with VDI 2230) Coefficient of friction class A Range for µG and µK 0. Zn/Ni. zinc flake coatings. screws with external hexalobular drive in accordance with DIN 34800 or socket cap screws in accordance with DIN EN ISO 4762 and “medium” bore in accordance with DIN EN 20 273 (in accordance with VDI 2230) 1790 . wax dispersions.08 to 0. waxes. greases. pastes Wax dispersions. zinc flake coatings. PE. hot-dip galvanised E ≥ 0. depending on the surface and lubrication condition of the screws or nut coat.10 Selection of typical examples for Material/surface Bright metal Black annealed Phosphate Galv. With the great number of surface and lubrication conditions it is often difficult to ascertain the correct coefficient of friction.14 to 0. Zn/Fe. Zn/Ni. graphite. so that the highest possible preload force with simultaneous low distribution can be applied. graphite. (The table applies to room temperature. coatings such as Zn/Fe.16 Tab. coatings such as Zn. liquefied wax. 6. Zn/ Ni. pastes Delivery condition (lightly oiled) None Oil None None B 0. PTFE.35 Austenitic steel Galv. wax dispersions With integrated solid lubricant or wax dispersion Solid lubricants. Zn/Fe. PI in solid film lubricants. If the coefficient of friction is not known exactly. PE. oils. the lowest probable coefficient of friction is to be reckoned with so that the screw is not overloaded. wax dispersions Solid lubricants such as MoS2. coatings such as Zn. Zn/Fe.2 for set screws with metric standard thread in accordance with DIN ISO 262.30 Galv.20 to 0. Zn/Fe.) 10 6.04 to 0. adhesive D 0. austenitic steel. graphite. Zn/Ni.24 Austenitic steel Bright metal. as top coats or in pastes. delivery condition MoS2.2% offset yield point Rp0. Mg alloys Lubricants Solid lubricants such as MoS2. Al and Mg alloys Hot dip galvanised Organic coating Austenitic steel C 0. PTFE.4 Assembly preload forces FMTab and tightening torques MA with 90% utilisation of the screw yield strength Rel or 0. Al. Phosphate Galv. coatings such as Zn. liquefied wax. 3 Coefficient of friction class B should be aimed for. head sizes of hexagon head screws in accordance with DIN EN ISO 4014 to 4018. as top coats or in pastes. zinc flake coatings Bright metal Black annealed Phosphate Galv. 3 7.0 59.9 9.0 19.3 72.9 12.9 41.8 49.6 24.799 2.2 31.2 12.957 4.7 36.1 96.8 10.137 7.041 915 1.4 11.7 11.1 26.549 7.7 24.3 28.08 2.9 12.672 2.791 3.5 24.1 14.8 61.6 85 121 142 109 156 182 137 194 228 157 224 262 207 295 345 252 359 420 314 447 523 368 524 614 443 630 738 Tightening torques MA in Nm for μK = μG = 0.136 1.287 1.2 23.2 49.134 2.346 0.3 56.9 121.7 101.4 12.8 10.9 104.2 12.3 16.9 12.8 21.5 45.3 12.787 2.0 11.0 4.5 107 152 178 136 194 227 170 242 283 196 280 327 257 367 429 313 446 522 389 554 649 458 652 763 548 781 914 0.9 17.3 18.057 798 1.6 34.959 1.0 106.5 15.8 10.627 6.840 2.9 12.0 13.4 50.6 88.8 26.092 901 1.5 72.381 2.958 5.161 3.5 9.9 12.5 7.3 32.569 5.597 5.7 18.9 68 100 116 117 172 201 187 274 321 291 428 501 415 592 692 588 838 980 808 1.679 2.7 9.0 102 145 170 130 186 217 162 231 271 188 267 313 246 351 410 300 427 499 373 531 621 438 623 729 525 748 875 0.8 139.3 44.7 27.8 8.3 22.759 3.7 28.5 22.081 4.6 62.9 52.9 24.4 12.8 10.664 0.4 72.089 3.3 38.8 115.500 1.631 3.5 17.458 1.7 26.6 16.6 10.4 16.1 42.274 2.017 1.1 20.9 17.0 8.8 24.8 10.9 12.6 22.3 50.3 17.14 3.9 8.123 5.6 34.482 3.7 6.8 10.4 14.3 77.054 4.6 3.2 43 63 73 73 108 126 117 172 201 180 264 309 259 369 432 363 517 605 495 704 824 625 890 1.2 27.9 14.208 4.9 14.8 37.4 104 149 174 134 190 223 166 237 277 192 274 320 252 359 420 307 437 511 381 543 635 448 638 747 537 765 895 0.928 2.7 96 137 160 123 176 206 154 219 257 178 253 296 234 333 389 284 405 474 354 504 589 415 591 692 498 710 831 0.9 8.755 1.4 6.6 116.347 1.9 12.348 3.4 14.6 6.5 12.246 1.385 3.246 1.1 124.2 59 87 101 102 149 175 162 238 279 252 370 433 360 513 601 509 725 848 697 993 1.6 5.3 6.9 12.0 55.9 8.0 40.2 7.4 26.4 7.6 18.2 66.8 10.5 5.053 1.9 8.1 16.961 3.2 29.7 6.6 31.7 142.322 2.6 27.1 11.6 8.2 15.1 64.5 6.8 36 53 62 63 92 108 100 146 171 153 224 262 220 314 367 308 438 513 417 595 696 529 754 882 772 1.9 12.1 44.8 10.637 6.0 10.8 99.0 13.9 8.1 13.4 21.100 1.498 2.2 7.1 22.5 30.345 3.0 8.6 7.6 11.9 8.3 45.0 21.7 40.8 10.9 4.7 10.6 43.6 19.497 2.9 8.9 8.2 14. 5 1791 10 .015 2.5 22.902 4.042 2.877 1.6 131.535 4.6 53.1 46.5 14.10 4.747 3.5 84.4 6.3 4.8 70.126 1.3 18.1 24.0 7.914 0.16 4.7 124.8 30.0 17.8 10.214 2.596 0.6 14.9 8.4 6.775 3.496 1.562 M5 M6 M7 M8 M10 M12 M14 M16 M18 M20 M22 M24 M27 M30 M33 M36 M39 Tab.9 8.2 15.5 13.151 1.Standard thread Size Strength Assembly preload forces class FMTab in kN for μG = 0.8 10.8 75.5 32.415 2.585 5.7 26.0 91.3 6.8 10.4 35.685 1.386 2.12 3.377 3.1 38.9 82.8 10.6 112.8 52.0 13.5 52.7 7.2 38.9 8.9 4.4 10.0 14.8 65.4 15.5 19.2 74.2 15.9 12.358 1.5 6.8 10.24 4.9 8.292 1.7 18.226 3.265 3.601 2.3 8.0 55.502 1.388 5.6 18.8 10.082 3.8 67.526 1.1 35.3 3.9 8.8 10.8 21.5 24.3 65.1 82.12 4.1 6.190 1.5 21.0 10.162 875 1.284 1.6 5.1 91 129 151 116 166 194 145 207 242 168 239 279 220 314 367 268 382 447 334 475 556 392 558 653 470 670 784 0.9 15.349 5.0 10.9 12.1 28.16 3.597 2.8 42.136 3.329 1.20 4.0 76.4 9.662 2.4 15.078 3.825 2.033 2.2 38.050 1.652 0.1 20.3 6.176 1.604 1.498 2.775 2.011 1.9 12.8 10.4 21.975 4.0 63.3 40.0 7.8 43.598 6.8 30.043 5.6 31.6 7.994 0.1 19.317 8.674 1.9 5.9 8.8 12.9 8.1 5.8 78.380 1.2 6.8 5.4 98.600 3.0 9.541 5.4 145.6 77.750 1.9 4.6 6.8 7.1 6.1 10.8 10.9 12.2 42.7 25.077 1.9 54 79 93 93 137 160 148 218 255 230 338 395 329 469 549 464 661 773 634 904 1.164 3.9 8.9 12.9 8.3 3.951 5.3 18.10 2.5 84.5 84.0 14.9 12.931 2.440 1.8 10.7 5.4 10.9 12.4 41.0 29.14 4.2 11.5 28.24 3.7 15.08 M4 8.893 3.1 21.598 3.6 31.3 13.9 12.7 25.0 45.8 51.9 60.135 3.2 15.6 45.9 8.754 2.20 3.607 2.1 7.0 48.0 57.0 9.7 135.0 32.8 9.6 7.5 27.2 48 71 83 84 123 144 133 195 229 206 302 354 295 421 492 415 592 692 567 807 945 714 1.0 20.1 28.304 1.2 90.2 10.9 12.5 26.5 14.9 61.930 4.4 99 141 165 127 181 212 158 225 264 183 260 305 240 342 400 292 416 487 363 517 605 427 608 711 512 729 853 0.428 2.5 11.3 75 110 129 130 191 223 207 304 356 325 477 558 462 657 769 655 933 1.4 18.778 3.3 58.923 2.2 27.9 118.5 80.9 26.7 59.1 86.6 12.2 106.8 10.153 1.6 25.7 33.8 43.6 36.5 7. 7 34.7 47.9 108.25 M12 x 1.2 52.280 1.234 1.5 M24 x2 M27 x 1.8 60.0 29.8 10.922 0.7 127.5 38.1 26.0 43.9 8.9 8.2 33.643 1.0 51.910 2.276 1.4 32.6 86.2 39.2 122.8 10.0 54.9 31.1 61.4 53 78 91 51 75 87 90 133 155 87 128 150 142 209 244 218 320 374 327 465 544 311 443 519 454 646 756 613 873 1.3 85 125 147 80 118 138 145 212 249 137 202 236 227 333 390 351 515 603 530 755 884 495 706 826 741 1.6 117 167 196 109 156 182 148 211 246 182 259 303 219 312 366 209 297 348 282 402 470 0.0 41.20 37.1 48.3 74.8 26.360 1.4 33.166 1.8 10.110 992 1.6 45.4 87.4 134.5 135.9 25.0 55.442 1.16 19.8 83.9 12. head sizes of hexagon head screws in accordance with DIN EN ISO 4014 to 4018.9 12.7 26.2 48.5 55.16 32.006 1.2 64.2 37.2 92.1 36.9 68.24 17.4 33.185 1.5 125.2 32.3 32.8 58.1 73.08 M8 x1 M9 x1 M10 x1 M10 x 1.2 for set screws with metric fine thread in accordance with DIN ISO 262.5 39.6 54.7 69.1 38.100 896 1.8 10.143 666 949 1.0 65.282 1.8 10.9 8.8 68.2 111.7 28.6 70.498 865 1.304 1.Assembly preload forces FMTab and tightening torques MA with 90% utilisation of the screw yield strength Rel or 0.5 43.1 72.7 34.7 48.1 55.9 8.6 62.9 33.0 70.9 12.5 8.9 29.5 146.445 2.114 1.9 12.8 45.856 1.7 85.2 56.9 8.12 26.0 63.0 47.6 73.9 12.08 19.5 31.20 18.6 33.9 12.4 105.7 40.9 12.9 40.055 1.8 93.080 1.4 46.0 46 68 80 44 65 76 79 116 135 76 112 131 124 182 213 189 278 325 283 403 472 271 386 452 392 558 653 529 754 882 686 977 1.9 45.1 39 57 67 38 55 65 66 97 114 64 95 111 104 153 179 159 233 273 237 337 394 229 326 381 327 466 545 440 627 734 570 811 949 557 793 928 822 1.8 10.9 46.25 M12 x 1.8 78.2 29.1 42.9 46.095 1.153 1.5 57.171 1.6 131.5 M18 x 1.4 41.4 28.9 65.6 154.0 45.6 49.1 66.0 46.9 28.9 44.3 48.1 22.9 78.153 899 1.8 33.5 40.5 M14 x 1.1 105 150 176 98 139 163 133 190 222 164 233 273 198 282 330 187 267 312 255 363 425 0.9 48.7 80.9 40.9 8.7 49.8 80.248 1.0 120 171 200 112 160 187 151 215 252 186 264 309 224 319 373 213 304 355 288 410 480 0.591 1.3 65.1 76.3 99.7 60.8 99.174 0.4 35.2 47.0 81.9 115 163 191 107 152 178 144 206 241 178 253 296 214 305 357 204 290 339 276 393 460 0.943 1.2 42.24 41.493 1.677 1.6 66.6 59.5 114.14 29.4 48.5 45.0 108.9 8.6 128.5 M18 x2 M20 x 1.8 38.4 27.3 44.4 97.5 70.8 10.8 30.1 122 174 204 114 163 191 154 219 257 189 269 315 228 325 380 217 310 362 293 418 489 0.5 116.720 3.7 34.5 80.9 25.10 20.232 1.311 1.14 19.6 66 97 113 62 92 107 111 164 192 107 157 183 175 257 301 269 396 463 406 578 676 383 545 638 565 804 941 765 1.3 63.9 12.4 69.2 31.2 63.9 8.0 44.1 84.7 150.5 38.2 60.8 50.3 32.661 1.12 20.6 59.9 8.8 10.5 82.8 10.5 M22 x 1.6 80.2 41.7 30.586 1.3 56.8 10. screws with external hexalobular drive in accordance with DIN 34800 or socket cap screws in accordance with DIN EN ISO 4762 and “medium” bore in accordance with DIN EN 20 273 (in accordance with VDI 2230) Fine thread Size Strength Assembly preload forces class FMTab in kN for μG = 0.183 10 1792 .9 67.10 22.2 28.8 10.4 59.5 90.5 91.8 57.4 47.0 24.326 769 1.8 10.275 995 1.6 46.2 73.9 12.1 85.1 32.4 79.2 157.4 44.2 99 141 166 92 131 153 125 179 209 154 220 257 187 266 311 177 251 294 240 342 401 Tightening torques MA in Nm for μK = μG = 0.409 0.2% offset yield point Rp0.1 48.5 66.0 23.9 12.6 68.9 12.5 M16 x 1.9 38.8 50.6 155.697 2.5 30.4 51.8 10.8 10.9 8.059 2.1 89.5 M24 x 1.9 12.433 1.1 104.3 43.0 47.2 44.8 10.4 54.9 74.2 93.6 27.5 39.9 8.5 50.2 28.6 56.370 0.1 63.2 51.022 796 1.9 21.9 12.3 28.090 1.7 35.8 78.3 60 88 103 57 83 98 101 149 174 97 143 167 159 234 274 244 359 420 368 523 613 348 496 581 511 728 852 692 985 1.8 95.9 12.417 1.777 2.9 38.9 8.0 55.9 12.9 8.1 112 159 186 104 148 173 141 200 234 173 247 289 209 298 347 198 282 331 269 383 448 0.4 76 112 131 72 106 124 129 190 222 123 181 212 203 299 349 314 461 539 473 674 789 444 632 740 660 940 1.417 2.9 8.654 0.7 89.133 1.3 143.4 45.413 1.867 2.658 955 1.828 0.858 2. 344 1.243 7.9 12.9 8.340 3.010 5.306 0.082 2.390 5.000 12.585 0.000 74.000 74.000 74.9 12.14 1.054 4.605 3.082 4.725 3.921 3.003 0.605 3.262 1.767 3.000 54.864 5.149 1.630 2.801 8.000 102.090 4.725 4.710 4. 6 6.483 3.829 2.2% offset yield point Rp0.116 1.10 276 393 460 347 494 578 425 606 709 512 729 853 607 864 1.8 10.470 2.555 2.797 2.000 102.08 806 1.489 2.8 10.100 MPa Gray cast iron Preload forces FVmax (N) M5 M6 M8 M10 M12 M14 M16 Tightening torque MA (Nm) M5 M6 M8 M10 19 42 85 M12 130 M14 230 M16 330 9.120 2.238 1.513 6.002 4.Size Strength Assembly preload forces class FMTab in kN for μG = 0.542 3.276 3.378 1.394 1.989 2.12 270 384 450 339 483 565 416 593 694 502 714 836 595 847 991 0.717 2.9 12.9 12.9 8.912 2.943 2.9 12.345 3.594 1.200 37.324 1.600 23.350 3.000 12.103 1.216 2.341 3.24 229 326 382 288 411 481 354 505 591 427 609 712 507 722 845 8.9 281 400 468 353 503 588 433 617 722 521 742 869 618 880 1.049 2.5 Tightening torque and preload force of • Safety screws with nuts • Flange screws with nuts With 90% utilisation of the screws’ yield strength Rel or 0.435 4.238 2.000 54.241 3.974 5.000 102.16 1.10 967 1.000 11 9.415 4.594 2.794 2.200 37.20 243 346 405 306 436 510 376 535 626 453 645 755 537 765 896 0.000 54.12 1.24 1.139 0.030 Tightening torques MA in Nm for μK = μG = 0.908 3.200 37.631 6.9 8.336 8.821 0.8 10.866 1.000 10 18 37 80 120 215 310 9.2 (according to manufacturer’s data) Counter material Locking screws strength class 100 and nuts strength class 10 Steel Rm < 800 MPa Steel Rm = 800– 1.641 4.965 3.927 2.600 23.322 2.882 4.383 6.711 6.137 3.767 3.151 7.481 1.011 0.590 1.692 4.986 2.000 9 16 35 75 115 200 300 Reference values 1793 10 .238 2.953 5.119 1.261 3.8 10.612 1.669 M27 x2 M30 x2 M33 x2 M36 x2 M39 x2 Tab.892 5.9 8.600 23.343 1.493 4.20 1.589 0.861 1.08 0.263 9.556 2.352 3.428 7.16 257 366 428 323 460 539 397 565 662 478 681 797 567 808 945 0.756 2.14 264 375 439 331 472 552 407 580 678 490 698 817 581 828 969 0.683 5.557 3.793 3.350 5.000 12.522 5.537 4.8 10.502 2.276 5.943 2. 5 30.0 776.6 20.0 272.40 5.5 58.0 FK 80 1.9 96.30 Preload forces FVmax.0 79.85 6.3 92.00 19.0 998.8 41.60 1.6.0 534.3 96.65 2.2 26.0 Tightening torque MA [Nm] FK 50 FK 70 FK80 1.0 183.80 11.0 966.0 159.80 6.85 1.0 205.0 114.6 35.70 2.0 232.3 34.0 88.0 224.0 13.94 3.45 1. [KN] FK 50 M3 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20 M22 M24 M27 M30 M33 M36 M39 0.96 6.30 2.0 50.90 1.0 76.0 284.59 4.0 135.0 724.0 174.2 33.0 275.7 32.0 Tightening torque MA [Nm] FK 50 FK 70 FK 80 1.6 18.0 141.13 16.08 2.0 FK 70 0.0 586.80 10.0 400.2 72.0 1.300 21.3 17.1 143.9 26.0 61.49 8.0 FK 70 1.189 1.0 86.25 5.9 69.83 2.0 370.0 58.4 67.0 29.0 842.95 3.0 488.3 73.00 1.98 11.0 506.4 44.9 24.0 106.0 69.3 50.0 61.10 1.93 5.12 1.19 4.0 89.90 14.30 2.1 15.0 374.0 148.2 41.6 Reference values for tightening torques for austenite screws in accordance with DIN EN ISO 3506 The following table shows the tightening torque required for an individual case in dependence on the nominal diameter.0 110.0 161.0 FK80 1.0 Coefficient of friction µges 0.6 44.7 72.0 142.0 FK 70 0.0 173.20 Preload forces FVmax.0 119.85 12.30 4.0 291.0 439.90 4.6 37.0 188.6 60.3 39.7 31.0 346.20 5.80 1.7 58.10 8.0 135.1 19.40 5.7 32.5 51.00 2.20 3.0 503.0 50.2 20.7 23.0 308.0 411.60 2.00 4.49 2.54 10.0 218.00 4.0 133.0 650.4 88.0 17.0 260.0 424.0 Tightening torque MA [Nm] FK 50 0.70 3.2 16.0 810.6 43.50 3.6 107.0 110.4 11.0 122.8 74.0 118.0 318.85 0.0 83.0 165.1 56.1 20. the coefficient of friction and the strength class (SC) as a reference value.0 39.0 494.0 582.0 FK 70 1.10 Preload forces FVmax.0 75.0 28.1 27.90 1.0 651.00 12.0 571.0 325.0 88.0 101.6 38.0 Coefficient of friction µges 0. [KN] FK 50 M3 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20 M22 M24 M27 M30 M33 M36 M39 0.2 23.0 41.9 56.85 13.0 21.0 929.0 187.0 680.7 78.75 7.58 11.5 25.0 FK 80 0.25 1.4 45. Coefficient of friction µges 0.0 114. 8 10 1794 .39 13.80 13.0 779.40 0.60 1.7 25.0 66.47 9.2 48.0 81. [KN] FK 50 M3 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20 M22 M24 M27 M30 M33 M36 M39 0.0 55.0 121.97 4.8 10.35 1.10 6.0 338.1 40.09 3.0 74.8 53.86 9.0 FK 80 0.80 6.14 9.0 Tab.0 227.4 59.40 3.8 56.9 33.0 108.4 34.0 117.0 608.60 3.0 91.0 47.26 3.0 100.50 2.10 2.2 5.0 421.60 8.0 94.4 36.7 26.32 13.00 1.59 4.0 75.85 6.24 7.0 144.6 21.0 162.553 25.10 8.0 102.0 1.5 118.0 245. line M12 and strength class 8.6 must be reckoned with.”) D) Preload force FVmin Example: In Table 5 in chapter 6 in column μG = 0. the tightening factor αA must be selected.7 How to use the tables for preload forces and tightening torques! The procedure is as follows: A) Determining the total coefficient of friction μges.9 KN in the area “Assembly preload forces”.14.14 for the line for M12 with strength class 8.8 read off the value for the maximum preload force FVmax = 41. C) Tightening factor αA (taking the tightening uncertainty into account) All tightening methods are more or less accurate. 4 (see Table 2 in chapter 6 “Reference values for the tightening factor . fast or slow tightening of the screw) • The distribution of the torque wrench itself. Depending on how the above-mentioned influences are controlled. Example: Selecting the screw and nut with surface condition zinc galvanised transparent passivation. Example: If a commercially available torque wrench with an electronic display is used.2) or of the yield point (Rel). Example: Hexagon head screw DIN 933.4 1795 10 . The maximum tightening torque is found with 90% utilisation of the 0. Preload force FVmin = FVmin = 29. strength class 8. Table 3 in chapter 6 is used to make the selection.4–1.2% offset yield point (Rp0. M12 x 50. a tightening factor αA = 1. depending on the surface or lubrication condition of the screws or nuts.. The selection is: αA = 1.14 (Note: the lowest probable coefficient of friction is to be reckoned with for the dimensioning of the screw so that it is not overloaded) B) Tightening torque MA max.. blue passivation: In Table 5 in chapter 6 look in the column for μG = 0.: Different coefficients of friction “μ” have to be reckoned with.9 KN 1.6. Now read off the desired value MA max = 93 Nm from the section “Tightening torque MA [Nm]”. without lubricant: µges = 0.8.g.8. galvanised.92 KN E) Control of the results You should ask yourself the following questions! • Is the residual clamping power sufficient? • Is the minimum probable preload force FVmin sufficient for the maximum forces that occur in practice? 41. This is caused by: • The large range of distribution of the friction that actually occurs during installation (if friction figures can only be estimated roughly for the calculation) • Differences in the manipulation with the torque wrench (e. obtained by dividing The minimum preload force FVmin is FVmax by the tightening factor αA. 5 4 4. If fasteners of equal value cannot be selected. galvanised. 9 6. heavy duty in accordance with ISO 8752 (DIN 1481) Up to 8 mm nominal diameter Up to 10 mm nominal diameter Material: Spring steel hardened from 420 to 560 HV 3.62 7.5 2 2.58 2.2 15.53 5. bright +++ +++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ + + – + +++ ++ + – + + + + + + + ++ +++ + – – +++ ++ ++ Steel.77 13 1.82 4. yellow chromated + + + Steel.32 9. galvanised. galvanised. Steel. blue pass.Steel.5 Fig.68 8. galvanised.5 111. [kN] Single-shear Two-shear 1 0.5 26 21. they must be of higher value than the parts to be connected.3 35 85. AV 3 0. yellow chromated –– –– –– –– + +++ ++ –– –– –– –– + + +++ + ––– ––– ––– ––– –– –– –– +++ +++ Highly recommended pairing ++ Recommended pairing + Moderately recommended pairing – Less recommended pairing –– Not recommended pairing ––– Pairing not recommended under any circumstances * This assumption applies with a surface ratio (component ratio of fastener to the part to be connected) between 1:10 and 1:40.16 4. Tab.9 Static shearing forces for slotted spring pin connections Slotted spring pins.7 1. + + + 20 Stainless steel A2/A4 6. 10 10 1796 Steel. galvanised.3 16 18 Fig.06 11.6 42.41 2.1 104. AU Nominal diameter [mm] Shearing force min. Pairing different fasteners/component materials with regard to contact corrosion Component material/surface* Fastener material/surface Stainless steel A2/A4 Aluminium Copper Brass Steel. black pass.5 5 6 8 10 12 52 13 57.2 140.5 280.79 1.19 3.5 14 72. black passivated Steel.1 171 Tab. galvanised.8 Pairing different element/contact corrosion The following rule applies for preventing contact corrosion: In each case fasteners must have at least the same corrosion resistance as the parts that are to be connected.4 17. bright Aluminium Copper Brass .38 6.1 144.35 0.7 70.1 115.3 222. blue passivated Steel. 88 3 2.8 0. AX Nominal diameter [mm] Shearing force min.2 5 9.4 3 3.46 18.82 2 1.6 31.02 62.76 5.62 76.5 0.2 6 9 7 21 8 24 10 20 40 11 22 44 12 24 48 13 33 66 14 42 84 16 49 98 18 63 126 20 79 158 Fig.93 9.37 4.6 0. 11 Spring-type straight pins.2 10 12 14 16 11.4 18 Tab.05 19. [kN] Single-shear Two-shear 0.5 4.5 3. AY Nominal diameter [mm] Shearing force min.64 6 8 39.54 4 4.90 Material: Spring steel hardened from 420 to 520 HV 1.40 1 0.85 61.9 6 13.77 7.2 1. AZ 4 4 8 10.5 2.24 89.Spring-type straight pins. 13 1797 10 .4 8. AW Nominal diameter [mm] Shearing force min.5 1.5 27 Tab.73 1.5 4. 12 Spring-type straight pins.5 3. coiled.5 2.8 5 5.2 0.3 Fig.52 3. slotted.91 1. light duty in accordance with ISO 13337 (DIN 7346) Up 8 mm nominal diameter Up to 10 mm nominal diameter Material: Spring steel hardened from 420 to 560 HV 4. heavy duty in accordance with ISO 8748 (DIN 7344) Fig.86 5 7.5 2.94 3.21 0.6 1.46 2 1.5 12 10.75 2. [kN] Single-shear Two-shear 2 1.5 0. [kN] Single-shear Two-shear Material: Spring steel hardened from 420 to 520 HV 1.3 0.29 2.12 44.1 Tab.2 152 15.75 1.74 3 3.57 3.14 2. standard design in accordance with ISO 8750 (DIN 7343) Fig.86 4 6.58 2.43 6.14 12.7 123.28 22.45 0. Previous drive systems AW drive Fig. AT 10 . 1798 Cross recess Z (pozi drive) in accordance with ISO 4757 Fig. • Greatest possible bearing surface of the bit in the screw drive → comeout. BA 6. • Longer service life through optimal fit. The even force distribution prevents damage to the surface protective layer and thus guarantees greater corrosion resistance. • Comeout = zero. AS Good force transmission through several points of application of force.10 Design recommendations for internal drives for screws Technical progress and financial considerations are leading worldwide to an almost complete replacement of straight slot screws by internal drives.F single-shear two-shear 2F F F F Fig. Hexagonal socket-screws have smaller widths across flats than hexagon head screws. AW drive Hexagonal socket Fig. AR AW drive system Advantages with regard to previous drive systems: • Improved force transmission by means of the conical multipoint head. which also means more economic designs because of smaller dimensions. • Optimum centring through the conical course of the bit. The four “tightening walls” in the cross recess. Length measuring method: the resulting lengthening of the screw is checked (measuring calliper). Fig. are vertical. whereby the lengthening of the screw has to be calibrated beforehand on a screw test stand. so that the subsequently applied further tightening angle of the nut can be determined easily. by means of screw lengthening).11 Assembly Torque method The required preload force is generated by the measurable torque MV. a torque wrench) must have uncertainty of less than 5%. 6. The tightening appliance that is used (e.g. whereby the screwdriver has trapezoid blade ends. Mark the position of the nut relative to the screw shaft and component clearly and permanently. The tightening appliances are to be adjusted as far as possible to the original screw assembly in a suitable manner (e. The pre-tightening torque is applied with one of the two methods described above. Retightening method: the connection is tightened first of all with the screwdriver and then retightened/checked with a precision torque wrench. The required further tightening angle must be determined by means of a method test at the respective original screwed connections (e. Fig. Pozi drive screwdrivers have rectangular blade ends. This can improve ease of assembly if the cross recesses are made optimally.g. with which the screwdriver is in contact when the screw is being screwed in. W 1799 10 . Angular momentum method The connections are tightened with the help of an impulse or impact driver with an uncertainty of less than 5%. AU Normal cross recess in which all walls and ribs are slanted. retightening method or length measuring method). Cross recess H (Phillips) in accordance with ISO 4757 Angle of rotation method Prerequisite is that the parts to be joined rest largely flat on each other. The remaining walls and ribs are slanted.g. 3. This may mean using expansion screws or long screws.1 Securing against loosening Screw assemblies can be prevented from loosening by means of suitable construction measures. In the latter case in particular. or increasing the preload force through screws with greater strength. reduces the surface pressure and prevents loosening.3 Methods of functioning 7. the hardness of the materials that are to be braced and any dynamic loads that may have an effect on the screw assembly must be considered when choosing a securing element. 7.1 General To select the right securing element it is necessary to consider the screw assembly as a whole. attention must be paid to the surface pressing on the support. or moulding a suitable hard washer to the head. or using such a washer.7. Sems screw 10 1800 . A flanged screw.2 Causes of preload force loss 7. In particular. SECURING ELEMENTs 7. Flange screw Lock screw Ribbed washer 7. Micro-encapsulation 1801 10 . or to use screws with micro-encapsulated adhesives. With the exception of slight unavoidable setting amounts the preload force in the connection is retained. With bonding in the thread it is possible to work with anaerobically bonding liquid plastic retention devices. Retention methods to prevent unscrewing are divided into • locking at the bearing • bonding in the thread Self-locking screw with serrated bearing Disc-lock washer Locking at the bearing takes place by means of the locking teeth that embed into the bearing material in the direction of unscrewing by means of tapered edges.2 Securing against loosening Loose-proof fasteners effectively prevent automatic unscrewing under the heaviest dynamic loads. or by means of symmetrical securing ribs that retain the preload force effectively on hard and soft materials. Screws with micro-encapsulated precoating are standardised in accordance with DIN 267/Part 27.3. Optisert insert 7.3 Securing against loss This group of securing devices comprises products that initially are unable to prevent automatic loosening. 1802 . Liquid adhesives 7. but after a more or less large preload force loss prevent complete unscrewing. so that the connection does not fall apart.3. All-metal lock nut Lock nut with plastic ring 10 The test results in three categories.4 How securing elements work The action of a securing element can be tested on a vibration test stand (Junker test). 7.2 Loss-proof fasteners The category of loss-proof fasteners comprises products that initially are unable to prevent automatic loosening. DIN 6904 • Toothed washers DIN 6797. 1803 10 .4. so that the connection does not fall apart. either with regard to loosening. Retention methods to prevent unscrewing are divided into • locking at the bearing • bonding in the thread Locking at the bearing takes place by means of the locking teeth that embed into the bearing material in the direction of unscrewing by means of tapered edges. • Spring washers DIN 127. or to use screws with micro-encapsulated adhesives. DIN 6906 • Serrated lock washers DIN 6798. DIN 128.9/10 A2-70/A2-70 Elastic if braced together To reduce setting max.8/8 10. or by means of symmetrical securing ribs that retain the preload force effectively on hard and soft materials. DIN 6905. for example.3 Loose-proof fasteners Loose-proof fasteners effectively prevent automatic unscrewing under the heaviest dynamic loads.1 Loosening Securing type Loose-proof Functional principle Securing element 7. the preload force in the connection is retained. Screws with micro-encapsulated pre-coating are standardised in accordance with DIN 267/Part 27. Use with screws in strength class ≥ 8.4. Information on application Screws/nuts Strength class Washers Hardness class 200 HV 300 HV Yes Yes No Yes No Yes Reduce the surface pressure if braced together Washer in accordance with DIN EN ISO 7089 DIN EN ISO 7090 DIN 7349 DIN EN ISO 7092 DIN EN ISO 7093-1 Heavy-duty locking washer in accordance with DIN 6796. profiled locking washer serrated contact washer 8. With bonding in the thread it is possible to work with anaerobically bonding liquid plastic retention devices. all-metal lock nuts or screws with a thread clamping insert in accordance with DIN 267/Part 28. DIN 6907 • Tab washers with external tab or two tabs DIN 432.8 is not advised. 7. With the exception of slight unavoidable setting amounts. This category includes.5 Measures for securing screws 7. or with regard to unscrewing.5. Thread grooving screws also belong to the group of loss-proof fasteners. but after an unspecified large preload force loss prevent complete unscrewing. nuts with a polyamide ring insert (lock nuts).4.1 Ineffective securing elements The products listed below have no securing effect whatsoever. 20 µm elastic force has to be aligned to the preload force. DIN 937 with cotter pins DIN 94 7. DIN 7980 • Wave washers DIN 137. DIN 463 • Hex castle nuts DIN 935. Use with electrical applications not recommended. The temperature limits for the adhesives that are used must be observed. With electrical applications there may not be any chip formation through all-metal nuts. lock nuts Profiled locking washers Tapered washer pair Ribbed washer Profile ring (material A2) Information on application To be used where screw connections with high preload forces are exposed to changing transverse loads. To be used where the primary aim of the screw assemblies is to retain a residual preload force and to secure the connection against falling apart. Inserts DIN 8140 Screws with plastic coating in the thread in accordance with DIN 267-28 10 1804 . Not on hardened surfaces. For electrical applications.2 Automatic unscrewing Securing type Unscrewing-proof Functional principle Blocking. DIN EN ISO 7042. Securing elements are only effective if they are arranged directly under the screw head and the nut. Adhesive Micro-encapsulated adhesive in accordance with DIN 267-27 Liquid adhesive Loss-proof Clamping Nuts with clamp DIN EN ISO 7040. If adhesives are used the threads must not be lubricated. If adhesives are used the threads must not be lubricated. in part braced together Securing element Lock screw. The temperature dependency must be noted for nuts and screws with a plastic insert. Use with electrical applications not recommended.7. Hardness of the contact surface must be lower than that of the contact surface of the screw and nut and of the elements that are tightened. Temperature-dependent.5. To be used where screw connections with high preload forces are exposed to changing transverse loads and hardened surfaces do not permit the use of locking fasteners. 1 HV connections for steel structures „HV“ is the marking of a screw assembly in steel constructions with high-strength screws in strength class 10. to increase the resistance against dynamic loads on parts or to limit the deformation of the total construction. Fig.9. In this way. Fig. Force transmis1805 10 . HV connections are therefore suitable without restriction for implementing all the following standard connections in steel construction. the operating forces are transmitted vertically to the screw axis. including with screws with short threaded portions (GVP). the possibility to bring the connection to a defined preload force with standardised methods. 1) The components affect the screw shaft like the blades of scissors. the contact surfaces have to be made friction grip by blasting or by means of approved friction grip coatings. such as bridge building. STEEL sTRUCTUREs 8. This type of connection can be preloaded (SLV) or implemented with dowel screws (SLP) or both (SLVP). high-grade corrosion protection through hot-dip galvanising with a zinc layer thickness of 60–80 μm. When the screw is tightened. sion here takes place through friction between the contact surfaces of the preloaded components. as shown in Fig. 2. Preloading the connection is necessary in particular with dynamic loads in the screw’s lengthways axis. because the connections are not designed with friction grip. in such cases it is often usual and practical to pre-stress the connections. which are used in individual cases. 1 The principle of operation of friction-grip preloaded connections (GV). Shear bearing connections (SL) transfer the force applied from the outside transverse to the screw axis through direct force transmission from the inner wall of the drill hole to the shaft of the screw (Fig. is fundamentally different. long-term corrosion protection is achieved even in aggressive atmospheres. Würth HV sets have good.e. in order to close gaps. „H“ stands here for high-strength. (Fig. i. 2 Operating forces in the screw’s lengthwise axis are of course permissible in all standard connections in steel construction and are accessible for verification of the strength by means of appropriate calculation formulae.8. 3). corresponding to the requirements for strength class 10. for example. For this purpose.9 and „V“ for „preloaded“. DIN 18800-1. While it is true that in over 90% of steel construction connections preloading is not necessary for technical reasons. i. 3 The galvanising is carried out accordance with DIN EN ISO 10684. only complete assemblies (screw.DIN Calculation DIN 18 800-1 design Execution Products DIN 18 800-7 DIN 7968. • Under the European standard. 8. In Parts 1 and 2. and HV fitting screws are found in Parts 4. for example. DIN 6915. 6. (DIN EN ISO 4014) DIN EN 14399-1/-2 DIN EN 14399-4 DIN EN 14399-6 DIN EN 14399-8 Tab. and these will be discussed separately below. Where the joints are preloaded in accordance with DIN 18800-7 with the help of the torque method. DIN 6916 DIN 7999 DIN EN DIN EN 1993-1-8 DIN EN 1993-1-9 DIN EN 1090-2 DIN EN 15048-1/-2 + tech. For this reason. irrespective of the applied corrosion protection. and there are transition periods here as well. the criteria Fig. The HV screws that are commonly used in Germany. this standard also describes the requirements and the procedure for acquiring the CE mark. The DIN pro-ducts were taken over to a great extent. nut and washer) from a single manufacturer are to be used. whereby the former DIN standards will continue to be applied during a transition period. so that there are only a few changes. The German standards have been retained only for ancillary products.2 HV screws. the same tightening torques are always applicable. nuts and washers In the course of the changeover to the European Construction Products Directive. in order to ensure the thread’s fit and to guarantee uniform tightening behaviour through special lubrication. and 8 of this standard. • The screw grip lengths table contained in the standard defines the screw grip length including the washers used (Table 2a and 2b). such as HV square taper washers in accordance with DIN 6917 and DIN 6918. 1: Changeover to European standards In future. In Europe. The cutting of the nut thread and the lubrication of the nuts under process conditions are carried out after hot-dip galvanising. In addition. DIN 7969 DIN 7990 DIN EN ISO 4014/4017 DIN 6914. and DIN EN 1993-1-9 for the verification of fatigue. product specs. the already existing standards for hexagon head screws such as DIN EN ISO 4014. taking account of additional stipulations that conform to the state of the art on manufacturing hot-dip galvanised screws. which represents a simplification in comparison with the previous status. Table 1 provides an overview of the changeover of the standards. DIN EN 1993-1-8 will apply to the calculation and design of joints. HV nuts are always treated with a special lubricant. The European standard DIN EN 15048 was created for non-preloaded. DIN EN 1090-2 will apply in future to the execution. The procedure for verifying compliance in accordance with Building Rules List A continues to apply. the products are marketable with the so-called “Ü” sign (conformity sign). low-strength screwing assemblies and describes the procedure and the requirements for acquiring the CE mark. The appropriate technical descriptions for this may be. harmonised European standards were drawn up for fasteners in steel and metal construction that have replaced the previous German DIN standards to a great extent. and the appropriate nuts and washers. 10 1806 . trade barriers may not exist or be established for products displaying the CE mark. The then unplated nut thread is corrosion protected after assembly by the zinc coating of the screw through cathodic corrosion protection. The harmonised standard DIN EN 14399 was drawn up for high-strength structural screwing assemblies.e. 05 12.6 15.84 33.95 20. washers and nuts 1) P = thread pitch (standard thread) 2) dw.9 11.16 22.4 5.55 14 13. nom.4 0. min.9 M22 2.2 12 11.4 0.3 12.5 0.64 M16 2 0. = sist Tab.84 38.7 4.55 8. max.47 1.5 0.20 15 14.0 45.7 4. The reason for this is the fact that DIN 18800 does not contain the above-mentioned special requirement in DIN EN 1993-1-8.7 4.8 6 5.1 15.9 9.87 1.7 20.1 17.16 3 2.4 0.7 24.56 2 50 49 5 4.5 36 35 4 3.3 M20 2.84 42.2 27 26.8 41 36 35 37 55. 2a 1807 10 . if a structure in accordance with DIN 18800 was planned.16 27.4 5. Sizes for HV and HVP screws1) Nominal size P1) c da ds min.6 24 22. max.85 17 16.17 1. the planned DIN HV assemblies can be replaced by others with the same nominal length in accordance with the DIN EN standards without the necessity of a realignment of the screwed positions.8 26 22 21.4 0.44 23 21.for calculating the screw grip length in accordance with the special requirements of DIN EN 1993-1-8 have been changed slightly.5 0.5 35.8 32 27 26.16 20.8 50.9 M24 3 0.75 6. nom.9 9.16 24.7 3.1 13.9 29.37 19 17.8 24 20 19. dw2) e k min.45 5.8 35 30 29. 10 Note: sizes before galvanising apply for hot-dip galvanised screws.2 22 21.3 9.16 4 3. M12 1.36 2 60 58.2 16 15.27 2 46 45 5 4.7 M27 3 0. min. max. min.4 6.4 0. max.max.3 16. max.3 39.9 8.28 1.1 14.8 28 24 23.4 0.6 29 27.3 16 14. m min.3 13 12.4 0. = max. min.6 19.7 4.3 20 18.4 0.47 1.3 18 16. min.1 23.6 22 20.56 10 9. so that there are further minor differences.75 0.84 29.16 30 46. However.7 M30 3.9 66.6 55.7 M36 4 0.95 24. min.91 8 7. kw r s h min.7 nom.5 41 40 4 3. max.05 15.25 10.03 13 12. nom.5 32 31 4 3. for HV and HVP screws1) Nominal length l 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 210 220 230 240 250 260 1) M12 11– 16 16– 21 21– 26 26– 31 31– 36 36– 41 41– 46 46– 51 51– 56 56– 61 61– 66 66– 71 71– 76 76– 81 81– 86 86– 91 91– 96 96–101 101–106 106–111 111–116 116–121 121–126 126–131 131–136 136–141 141–146 146–151 151–156 156–161 161–166 M16 M20 M22 M24 M27 M30 M36 12– 17 17– 22 22– 27 27– 32 32– 37 37– 42 42– 47 47– 52 52– 57 57– 62 62– 67 67– 72 72– 77 77– 82 82– 87 87– 92 92– 97 97–102 102–107 107–112 112–117 117–122 122–127 127–132 132–137 137–142 142–147 147–152 152–157 157–162 18– 23 23– 28 28– 33 33– 38 38– 43 43– 48 48– 53 53– 58 58– 63 63– 68 68– 73 73– 78 78– 83 83– 88 88– 93 93– 98 98–103 103.Screw grip length Σtmin.108 108–113 113–118 118–123 123–128 128–133 133–138 138–143 143–148 148–153 153–158 158–163 168–173 178–183 188–193 198–203 208–213 218–223 The screw grip length Σt comprises the two washers as well Tab. and Σtmax. 2b 10 1808 .108 108–113 113–118 118–123 123–128 128–133 133–138 138–143 143–148 148–153 153–158 158–163 163–168 168–173 173–178 183–188 193–198 203–208 213–218 223–228 233–238 22– 27 27– 32 32– 37 37– 42 42– 47 47– 52 52– 57 57– 62 62– 67 67– 72 72– 77 77– 82 82– 87 87– 92 92– 97 97–102 102–107 107–112 112–117 117–122 122–127 127–132 132–137 137–142 142–147 147–152 152–157 157–162 162–167 167–172 172–177 182–187 192–197 202–207 212–217 222–227 232–237 29– 34 34– 39 39– 44 44– 49 49– 54 54– 59 59– 64 64– 69 69– 74 74– 79 79– 84 84– 89 89– 94 94– 99 99–104 104–109 109–114 114–119 119–124 124–129 129–134 134–139 139–144 144–149 149–154 154–159 159–164 164–169 169–174 179–184 189–194 199–204 209–214 219–224 229–234 36– 41 41– 46 46– 51 51– 56 56– 61 61– 66 66– 71 71– 76 76– 81 81– 86 86– 91 91– 96 96–101 101–106 106–111 111–116 116–121 121–126 126–131 131–136 136–141 141–146 146–151 151–156 156–161 161–166 166–171 176–181 186–191 196–201 206–211 216–221 226–231 39– 44 44– 49 49– 54 54– 59 59– 64 64– 69 69– 74 74– 79 79– 84 84– 89 89– 94 94– 99 99–104 104–109 109–114 114–119 119–124 124–129 129–134 134–139 139–144 144–149 149–154 154–159 159–164 164–169 174–179 184–189 194–199 204–209 214–219 224–229 43– 48 48– 53 53– 58 58– 63 63– 68 68– 73 73– 78 78– 83 83– 88 88– 93 93– 98 98–103 103. 1 NR. interaction verification has to be carried out in accordance with the requirements of DIN 18800-1.55 for HV screws in strength class 10. Tables or appropriate software are usually available for calculation purposes. when the smooth shaft is in the shear joint.d is VI.R.44 for HV screws in strength class 10.R.d = If a tensile force and a shear force affect a screw simultaneously.R.k Characteristic tensile strength of the screw material.d = A · aa · u.kw X Ø ds Ød Serial no e In accordance with DIN 18800-1:2008-11 the calculation values for the hole face loads VI may not exceed the limit hole face forces VI.1 HV joints in accordance with DIN 18800-1 (2008) The calculation values for the shearing stress Va may not exceed the limit shear forces Va. r 1809 10 .d f Va. Tension cross-section ASp.9 = 1. when the smooth shaft is in the shear joint. 4 Screw in accordance with DIN EN 14399-4 Washer in accordance with DIN EN 14399-6 = t · dSch · al · c Ø dw Ø da fz. 0. 8.d is Va.R.b. VI ≤1 VI. Because of the yield point ratios of strength class 10.R.R.b.b.9. in particular on the distances of the screws from the edges of the components and from each other. 5 8.k for FK 10.k Characteristic yield point of the component material γM = 1. when the threaded part of the shaft is in the shear joint.R.d in accordance with DIN 18800-1:2008-11. aa 0. when the threaded part of the shaft is in the shear joint.k γM Nut in accordance with DIN EN 14399-4 h m Detail X Screw grip length Σt Fig.R.k γM A Shaft cross-section Asch.3.d 15° to 30° k ls lg l u s Thread end in accordance with DIN 78-K u = incomplete thread = max. Va ≤ 1 The limit shear force Va. The limit tensile force is therefore calculated as: ASp · fu. depending on the hole pattern fy.d The limit hole face force VI.k 1.R. DIN 18800-1 differentiates cases for the calculation of the limit tensile force under the pure tensile load on the screws.000 N/mm² 1.9.3 Construction information and verifications for HV joints accordance with DIN 18800-1 and DIN EN 1993-1-8.1 part safety coefficient for the resistance Factor a1 depends here on the geometry of the completed screwed connection.1 part safety coefficient for the resistance With t thickness of the component dSch Shaft diameter of the screw a1 Factor for determining the hole face endurance.d. 2 P Fig.d = t · dSch · σI. fu.9.25 · γM ASp Tension cross-section fu.25 = Coefficient for the increased security against tensile strength γM = 1.d = A · τa. the failure in the thread is decisive for HV screws. for HV screws: 1000 N/mm2 γM = 1.b.R. 9 Compared with DIN 18800-1 Not classified.8 or 10. the loads Vg may not exceed the boundary sliding forces Vg. interaction verification has to be carried out for GV and GVP connections in the same way as for SL and SLP connections. In the simple case of friction-grip connections without external tensile load the approaches in accordance with DIN and EN are also similar.8 or 10. Shear/bearing resistant and friction-grip connections Category A Shear/bearing connection B Friction-grip connection (GdG) C Friction-grip connection (GdT) Tensile loaded connections Category D Not preloaded E Preloaded Remarks No preloading necessary. however. if an external tensile force acts (1.0 In addition. 10 1810 .R. In this case. If the shaft is in the shear joint the stress resistances are approximately the same.d 8. a significant difference has to be mentioned at this point that also has effects on the applicable preloading method.8 or 10.2 HV joints in accordance with DIN EN 1993-1-8 The European standard classifies the screw assemblies in accordance with Table 3 and makes a fundamental difference depending on the direction of the external force. but verification criterion indicated Remarks No preloading necessary. μ · Fv · (1 – whereby: µ is the coefficient of friction after pre-treatment of the friction surfaces in accordance with DIN 18800-7 Fv is the preload force in accordance with DIN 18800-7 N is the tensile force falling pro rate on the screw γM = 1.R. The verification of bearing stress differs here in the approach from the procedure in accordance with DIN 18800-1 so that transmission of calculation results or table values is not possible.6 to 10.3. the stress resistance in accordance with EN is greater than in accordance with DIN.9 preloaded.With friction-grip connections (GV and GVP). but in most cases an advantage. If the thread is in the shear joint they are the same.R.15 · γM) on the HV screw. if no external tensile force acts on the (1.d is μ · Fv . Vg. recalculation in accordance with the requirements of DIN EN 1993-1-8 is necessary.9 High-strength screws SC 8.d in the boundary state of usability Vg ≤1 Vg.d = N ) Fv Vg. strength classes 4.R.9 High-strength screws SC 8.d = .R.15 · γM) HV screw. In many cases.9 preloaded GV or GVP GV or GVP Tab.6 to 10. Compared with DIN 18800-1 GdG SL or SLP GdT SL or SLP SL or SLP GV or GVP (net) High-strength screws SC 8. In the case of HV screws under tensile load in the screw’s lengthwise axis the calculation approach hardly differs at all from that in the DIN standard and the results are approximately the same. strength classes 4. 3 The boundary sliding force Vg. Verification of shearing off of the screws in accordance with EN differs only slightly and has a similar structure from the theoretical aspect. Screw assemblies that were preloaded with the help of the torque method are accessible very easily for a check by applying a test torque that is 10% greater than the tightening torque. this can be the preload force level in accordance with DIN 18800-7. Tab.C* is permissible for all screw assemblies that are not friction-grip calculated and are to be preloaded for other reasons. and at least 5% of the assemblies for the connection with connections that are mainly loaded at rest (with connections with less than 20 screws at least 2 connections.DIN EN 1993-1-8 stipulates a higher preload force level for friction-grip connections (and only for these) than is usual for preloaded HV joints in accordance with DIN 18800-7. The assembly values may be taken from DIN 18800-7 and are shown in chapter 8. or 1 connection).7 fub AS Because of friction distributions.4 Assembly 8.4. the tightening torque is always the same irrespective of the delivery condition. Measures for checking are not required for connections that are not systematically preloaded. The preload force should amount to 70% of the tensile strength of the screw: Fp. In the case of connections that are preloaded systematically at least 10% of the assemblies for the connection are tested in the case of connections that are not mainly loaded at rest. Torque method Applicable tightening torque MA for achieving the standard preload force Fv [Nm] Surface condition: hot-dip galvanised and lubricateda and as manufactured and lubricateda Standard preload force FV [kN] (corresponds to Fp. The assembly is to be checked after the marking (situation of the nut relative to the screw shaft) from the side from which tightening took place. 4: Preloading through torque example to increase the fatigue resistance. For example. 1811 10 .1 Assembly and test in accordance with DIN 18 800-7 The torque method is to be used preferably for preloading. so that alternative methods have to be applied that reduce the influence of the friction. This means that all preloaded screw assemblies in accordance with DIN EN 1993-1-8 that are not friction-grip preloaded may be preloaded with the standard torque method for screw assemblies. the preload force amounts to 70% of the screw yield point. for Dimensions 8. a lower preload force level Fp.C* = 0.7 x fyb · AS) 1 2 3 4 5 6 7 8 a M12 M16 M20 M22 M24 M27 M30 M36 50 100 160 190 220 290 350 510 100 250 450 650 800 1250 1650 2800 Nuts treated in the delivery condition by the manufacturer with molybdenum sulphide or similar lubricant.C = 0. Fp. The standard preload force in accordance with Table 4 corresponds to 70% of the screw yield point and is therefore generated by applying a tightening torque MA. this preload force level is no longer reliably achievable with the torque method.7 fyb AS That is.C * = 0. In contrast to earlier rules. However. The tightening torque is the same here for all surface conditions of the fasteners.4. following corrections the complete execution of the whole connection must be monitored. the angle of rotation method and a combined method. 5 Other methods referred to in the standard are the momentum method. which are only mentioned here because they are seldom used. 10 1812 .The procedure in Table 5 that is used depends on the further rotation angles that occur during the test. If necessary. If an unequivocal test is not possible (other methods used). the wording of the standard is to be used. the operation must be monitored for at least 10% of the connections. If deviations from the defaults specified in the respective method test are found. Tab. Checking the preload force with standard preload forces Further angle of rotation < 30° 30° to 60° > 60° 1 Evaluation Preload force was sufficient Preload force was conditionally sufficient Preload force was not sufficient Measure None Leave the assembly and test two adjoining connections in the same joint Change the assembly1 and test two adjoining connections in the same joint These checked fasteners may only be left in the construction with SLV or SLVP connections that are loaded mainly at rest without additional tensile loads. • After tightening.2 Assembly in accordance with DIN EN 1090-2 With all preloaded connections that are not designed friction-proof the preload force is 70% of the screw yield point and thus the torque method in accordance with DIN 18800-7 is applicable in conformity with the EN without restriction. • Up to 3 washers with a total thickness of 12 mm are permissible on the side of the assembly that is not turned to compensate for the screw grip length.C if there is no recommendation from the manufacturer. whereby the combined method appears practicable here. the necessary further angle of rotation should be determined in experiments.4.7 fub AS is stipulated in accordance with DIN EN 1993-1-8.7 · fub ·AS [kN] Pretightening torque MA [Nm]1) M12 59 75 M16 110 190 M20 172 340 8. the screw thread should usually project over the nut by a complete turn of a thread. HV screws. nuts and washers must be protected from corrosion and dirt. Table 6 indicates the tightening parameters for the combined method in accordance with DIN EN 1090-2.C = 0. Combined method Dimensions Preload force Fp.C = 0. • If a preloaded assembly is unscrewed subsequently it must be dismantled and replaced with a new one.8.1 = 0.13 d Fp. In the cases in which the connection is designed friction-proof. 6: Preloading with the combined method 1813 10 .5 Special information for using HV assemblies • When stored. a preload force to: Fp. • If preloading is carried out by turning the screw head. After this the connections are then tightened by the further angle of rotation stipulated in the standard. M22 212 490 M24 247 600 M27 321 940 M30 393 1240 M36 572 2100 Further angle of rotation or revolution dimension for screw grip length Σt Total nominal thickness “t” of the parts to be joined (including all lining plates and washers) d = screw diameter 1 2 3 t < 2d 2d ≤ t ≤ 6d 6d ≤ t ≤ 10d Further angle of rotation 60 90 120 Further revolution dimension 1/6 1/4 1/3 Note: I f the surface under the screw head or the nut (taking account of any square taper washers that are used as well) is not vertical to the screw axis. 1) Example of manufacturer’s recommendation Tab. This makes it necessary to apply other methods. The connections are tightened here with a pre-tightening torque that is recommended by the screw manufacturer or can be estimated with Mr. a suitable lubricant must be applied to the head and a method test carried out. • Reduction of radial tensions Construction of thinner walls. Over 150 different dimensions are manufactured according to standards of the automotive industry. DIRECT SCREWING INTO PLASTICS ANd METAL 9. With its WÜPLAST® product line the Würth Industrie Service GmbH & Co. Advantages here are found among other things in the fields of weight reduction. Fasteners constructed for screwing into plastics in particular enable greater process security in comparison to other screw types through their lower flank angle and greater thread pitch. possibly savings of costs and weight No damage to the screw dome • Greater overlapping between the thread flanks and material greater pull-out forces increase the process security. 10 1814 30º P . the ability to be unscrewed and low-cost procurement. The direct screwing into plastics with thread-forming metal screws offers advantages over other connection methods through its economic assembly possibilities. increased chemical resistance and in recycling components.9. KG offers its customers an in-stock range of thread-forming metal screws for the application in plastics.1 Direct screwing into plastics The use of plastics is gaining in importance through new application possibilities. Thread geometry 30° angle Optimised thread pitch • Highly self-locking Independent loosening of the connection is less likely • Material protection Greater loadability of the screw assembly Optimised core diameter • No material jam/improved material flow No damage to the material and therefore enhanced assembly security • Lower tightening torques Secure connection because of the greater difference between screwing torque and thread stripping torque The reliable multiple connections of WÜPLAST® products is secured through the combination of these features. 82x d 0.7x d 1.77x d External Ø mm 2x d 2x d 1.8x d 0.8x d 1.Tube design: Construction: The properties of WÜPLAST® screws enable the tube to be constructed with thin walls and flat.85x d 1.7x d 1.7x d 1.8x d 0.85x d 0.75x d 0.75x d 0.8x d 2.85x d 1.2x d* 2x d 1.85x d 1.8x d 1.8x d 1.8x d 2x d 1.8x d 1.7x d 1.75x d 0.8x d 0.6-GF30 PA 6 PA 6-GF30 PA 6.72x d 0.78x d 0.9x d * TnP test ** TnBP test materials sensitive to tension cracking 1815 10 .85x d 0.8x d 0.75x d 0. Material ABS ASA PA 4.75x d 0.85x d 1.75x d 0.7x d 1.7x d 2x d 2x d 2x d 2x d 2.85x d 2x d 1.75x d 0.5x d 2.7x d 2.85x d 0.95x d 2x d 2x d 2.8x d 1.6-GF30 PA 30GV PBT PBT-GF30 PC PC-GF30 PE (weich) PE (hart) PET PET-GF30 PETP PETP 30GV PMMA POM PP PP-TV20 PPO PS PVC (hart) SAN Acrylonitrile/butadiene/styrene Acrylonitrile/styrene/acrylic ester Polyamide Polyamide Polyamide Polyamide Polyamide Polyamide Polyamide Polybuteneterephthalate Polybuteneterephthalate Polycarbonate Polycarbonate Polyethylene Polyethylene Polyethylene terephtalate Polyethylene terephtalate Polyethylene terephtalate Polyethylene terephtalate Polymethylmethacrylate Polyoxymethylene Polypropylene Polypropylene Polyphenylenoxide Polystyrene Polyvinyl chloride Styrene/acrylonitrile Hole Ø mm 0.7x d 1.8x d 1. Relief hole: The relief hole at the upper end of the drilled hole reduces tension overlapping and thus prevents the tube from bursting.85x d 2x d 1. The tube geometry is to be adjusted to the different materials.5x d 2x d 2x d 2x d Recommended screwing depth mm e 2x d 2x d 1.8x d 1.2x d 2x d 1.2x d** 2x d 2x d 1.8x d 1.8x d 0.6 PA 6.78x d 0.7x d 0.8x d 0.6 PA 4.8x d 0.7x d 0.73x d 0.85x d 1.2x d* 2.7x d 1. At the same time it serves to guide the screw during assembly.85x d 0.8x d 0. 2. The screwing speed is to be selected between 300 rpm and 800 rpm. These screws groove the counterthread themselves without cutting. e. which is smaller in comparison with tapping screws. or in These screws are usually case-hardened.g. steel..Assembly instructions Schematic curve of the tightening process lightweight construction materials up to 140 HV10 or in accordance with a tensile strength of 450 MPa. 4 x P thread pitch in accordance with DIN 7500. Duo-Taptite or Taptite 2000 are frequently found on the market today. the screws form a normal nut thread without cutting into which a conventional screw can be screwed. greater speeds lead to damage to the plastic and to a disproportionate reduction of the preload force. which means that the surface is extremely hard and the core is very ductile. screws such as Taptite. A secure directly screwed plastic joint can only be made with torque-controlled and rotation-angle controlled assembly equipment. For placing in the core removing hole the screw thread is conical over max. However. The following two tables provide good points of reference. Both the tube design and the tightening torque are to be checked in practice on the components. 10 1816 . 9. 9. The thread pitch. The required tightening torque can be determined theoretically with the following equation: MA = ME + 1/3 … 1/2 (MÜ – ME) The screwing and the thread-stripping torques are to be determined in experiments.1 Metric thread grooving screws These screws are used in clearance holes and very frequently in tapping holes (aluminium or zinc diecasting).2. To make thread grooving easier the screw cross-sections are specially formed (trilobular) over the whole length or at the screw end only. Tightening torque: Necessary for a reliable screwed joint is a great difference between the screwing and the thread-stripping torques.2 Screw assemblies for thread-grooving screws in accordance with DIN 7500 (Gefu-1 and Gefu-2) The ideal drilling diameter for the tapping holes is to be determined through experiments. The DIN 7500 screw is the oldest and most widespread design here and defines the thread and the technical delivery conditions. They can be used in ductile metals such as. and the high thread engagement give the screws a certain amount of security against independent loosening. 9. Because of the heat effect. When driven in.2 Direct screwing into metals Thread forming screws for metals are grooving screws with metric threads and tapping screws. 5 7.55 5.5 4.0 3.4 5.5 5.25 7.65 5.0 3.5 4.5 5.7 2.65 4.0 7.6 3.5 1.6 3.0 5.8 2.7 2.55 4.7 2.6 4.5 3.45 5.55 4.55 5.5 4.5 4.7 3.7 1.75 2.25 7.45 5.5 4.8 2.5 4.75 2.5 4.0 5.5 4.5 5.6 3.5 3.65 3.6 3.5 4.75 2.45 5.6 3.65 3.5 4.65 4.5 4.6 4.75 2.75 2.5 4.45 5.25 7.65 3.5 4.5 4.4 5.55 4.2 3.5 4.25 7.75 2.25 1817 10 .4 5.5 4.45 5.25 7.2 2.2 3.5 5.5 4.5 4.65 4.75 3.75 2.65 4.4 5.5 4.4 5.55 5.25 7.5 4.65 3.6 4.45 5.5 3.4 5.2 1.75 2.75 2.25 7.45 5.5 6.4 5.5 4.45 5.4 5.65 2.6 3.6 1.Gefu-1: Recommended tapping holes for cold malleable materials in dependence on the screwing length Thread d M3 M4 Cu M5 St Al Cu M6 St Al Cu Material thickness Recommended tolerance field of the screwing St Al Cu St Al length 1.5 8 to ≤ 10 >10 to ≤ 12 >12 to ≤ 15 2.6 1.4 5.75 2.4 5.7 2.65 3.65 4.6 3.7 3.6 3.5 4.0 1.6 4.6 3.5 4.5 4.5 5.65 3.25 7.4 5.75 2.25 7.55 5.5 5.2 1.5 4.25 7.5 5.7 1.25 7.5 4.25 7.25 7.7 3.6 3.55 4.0 2.5 4.75 2.5 4.7 2.7 3.6 3.5 4.5 4.0 1.5 4.5 4.45 5.5 5.5 4.4 5.3 6.5 4.45 Gefu-2: Recommended tapping holes for ductile materials Thread d M5 M6 Al Cu M8 St Al Cu Material thickness Recommended tolerance field of the screwing St Al Cu St length 1.5 4.6 3.75 2.45 5.6 3.2 2.55 4.5 5.0 2.45 5.5 1.45 5.45 5.7 2.25 7.55 3.45 5.7 2.5 4.65 4.5 5.45 7.5 4.0 6. 3 2.65 4.55 5. Strength properties.65 4.65 4.55 approx.5 5.7 3.0 Thread nominal diameter M2 0.5 5.4 5.3 7.5 5.6 4.5 Material thickness Recommended tolerance field of the screwing St Al Cu St length 4.5 7.8 M3.7 1.45 5.5 4 2. HB max.3 M4 0.45 5.6 4.25 3.65 4.4 0. tapping hole geometry When the screw length is selected.0 5.35 7.65 M8 1.55 5.8 7.5 5.5 Al 7.65 4.5 5.5 7.4 7. A = Max.6 4.5 5.0 5. light metal.6 2.3 7.55 4.65 4.55 4.55 M8 St 7.5 Cu 7.45 5.85 M2. A2 screws can normally only be driven into lightweight metal.0 10.4 7.5 5.5 5.75 2.0 6.65 4.7 M6 1 12 16 5.5 5.65 4.4 7.6 4.65 4.5 7.4 7.25 2.5 5.0 14.5 0.5 7. nonferrous heavy metal).3 7. HB max.5 5.35 7.0 7.5 7.35 7.3 5. tolerance js 16 s = Material thickness Fig.4 7.0 1818 .2.45 5.65 3.35 7.65 4.5 7.6 4.6 4.6 3.35 7. Fracture torque min.Thread d M5 M6 Al 5.5 7. 135.4 4.25 29 29 7. 80% of the fracture torque Tapping hole diameter d – H11 for steel. the length of the non-bearing conical screw end has to be taken into account! With harder materials the hole diameters are to be determined in experiments.65 4.4 7.5 5.0 6.3 7.5 7.4 7.5 1. drilled and stamped 10 16.25 7.3 7.5 7. AB Technical data Thread pitch P [mm] Tightening torque max.3 7.5 0.4 3.4 7.5 4. [kN] Material strength s [mm] 2 and less 4.65 4.5 5.45 5.15 3.45 1 2.5 5.6 4.55 Cu 5.4 7.4 7.5 6.45 7.5 5.55 4.7 3. 4 P B = Possible bearing thread length C = Total length. DIN 7500 screws form their own counterthread without cutting through plastic deformation of the base material (steel.3 7.3 7.6 4.3 Direct screwing into metals with thread-grooving screws in accordance with DIN 7500 When they are driven in.5 5. [Nm] Tensile force min.0 12.5 5.2 3.5 5.8 1. 135.3 7.6 4.5 1.65 4.65 4.6 4.3 6.6 5.55 5.35 M3 0.4 7.7 2.5 8 to <= 10 >10 to <=12 >12 to <=15 4.7 2.4 7.5 5.65 4.3 7.75 M5 0.4 7 3.0 8.1 11.55 9.65 5.5 4. 5 –0.11 3.0 4 M5 5. d2.8 +0.37 5.09 14 +0.5 –0.24 7.075 11 +0.3 4.3 +0.0 3.2 2.5 3. with increased conicity for roundings advantageous for casting.64 +0 –0. tightening angle 1° Fig.0 5 M6 6.48 +0 –0. prevention of material bucking.9 +0.23 +0 –0.Tapping holes for diecasting All recommendations must be checked by means of practical assembly experiments.2 +0.35 +0 –0.0 6 M8 8. screw centring. AC Thread nominal diameter dH12 [mm] d1 [mm] d2 [mm] d3 [mm] Tolerances for d1.77 4. strengthening of the mandrel.6 +0 –0.27 +0 –0.86 2. max.36 2.76 +0 –0. d3 in [mm] t1 [mm] t2 [mm] Tolerances for t2 in [mm] t3 [mm] M2.5 2.5 4.6 –0.4 5.7 3.06 5.69 5.075 6.4 7.075 9.78 3.5 M4 4.3 3.32 3.5 –0.67 2.06 6 +0.2 –0.075 7.0 2.0 8 Variable.0 3 M3.63 7.5 M3 3. and adaptation to low-cost standard screw lengths.5 –0.2 2. General t1 [mm]: Upper hole range. t2/t3 [mm]: Bearing tapping hole range.7 2. minimum 1x thread pitch P 1819 10 .54 3.2 –0. 1 Tapping screw assemblies The following examples for screw assemblies apply for tapping screws with threads in accordance to DIN EN ISO 1478. 3 to 6 can be used. If this condition is fulfilled. This applies in particular when several plates are screwed together and hole misalignment must be expected.3.3 Tapping screws 9.9. Minimum value for the total thickness of the plates to be screwed together The plate thicknesses of the parts that are to be screwed together must be greater than the increase in the thread of the selected screw. because otherwise sufficient tightening torque cannot be applied because of the thread run-out under the screw head. tapping screw assemblies as shown in Figs. 10 1820 . Tapping screws with form C with a point (also known as a pilot point) are used preferably. 4: Tapping hole drawn through (thin plates) Fig. 1: Simple screwed joint (two tapping holes) Fig. 2: Simple screwed joint with through hole Fig. widened (thin plates) Fig. 5: Prestole screwed joint Fig. 3: Tapping hole.Fig. 6: Screwed joint with tightening nut 1821 10 . 1 3.4 2.2 3.5 2.1 3.6 3.7 2.4 2.9 2.7 2.5 x minimum fracture torque • Screwed joint in direction of stamping only • Select stamped holes possibly 0.6 2.8 1.0 3.6 1.3 3.9 3.7 2.3 3.5 3.4 2.5 3.5 1.6 3.7 2.7 2.7 1.0 3.0 2.2 2.7 1.7 1.5 3.2 2.3 2.9 3.2 3.2 2.7 2.7 1.8 2.1 2.7 2.8 1.5 2.4 2.2 3.2 2.2 3.0 3.4 2.4 3.2 3.0 3.1 3.9 3.4 3.9 1.9 2.8 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 1.9 1.7 2.5 2.4 3.3 2.2 Plate thickness s 1.7 2.0 3.7 2.2 2.2 2.2 3.2 3.5 3.9 2.2 3.7 1.2 2.9 3.8 1.5 1.7 2.2 2.0 1.7 1.0 2.5 2.4 3.8 3.7 1.5 2.5 1.8 1.4 1.4 3.3 2.8 2.6 3.4 2.5 1.2 2.7 1.9 1.0 2.4 3.Tapping hole diameters The tapping hole diameters shown in the following tables apply subject to the following preconditions: • Simple tapping screw assembly in accordance with Fig.3 3.3 3.6 3.9 2.7 1.4 3.8 3.1 3.3 3.3 3.7 1.7 1.7 2.2 2.2 2.7 10 1822 .5 1.2 3.4 3.9 2.0 3.0 2.3 2.6 2.2 2.2 2.2 3.0 3.9 1.5 Tapping hole diameter db for thread size ST 4.7 1.7 1.1 3.0 3.7 1.2 2.0 3.3 2.2 2.7 2.2 3.7 1.6 2.8 1.2 2.7 1.8 1.8 2.3 3.2 3.0 3.5 3.2 2.8 1.2 3.4 2.9 3.2 3.6 2.2 2.6 3.2 2.3 3.1 Tapping hole diameter db for thread size ST 3.8 2.6 3.2 3.2 2.3 3.1 3.4 3.3 3.4 2.2 2.2 2.3 1.7 1.4 3.7 1.1 3.8 2.7 2.1 1.9 1.1 2.5 3.5 3.8 1.9 2.7 1.1 3.7 2.4 3.8 1.2 2.0 3.2 3.6 1.8 1.2 3.0 3.7 1.8 2.5 Tapping hole diameter db for thread size ST 2.9 2.1 3.2 2.7 1.2 3.9 2.9 1.8 1.4 3.2 1.2 3.4 1.3 3.4 3.2 2.7 1.9 3.7 1.8 2.2 3.7 1.1 3.2 2.5 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 3.7 2.9 2.0 3.7 1.7 1.8 2.4 1.8 2.5 2.1–0.7 1.8 1.9 2.7 1.0 3.9 3.0 3.7 1.7 1.4 3.1 3.1 3.9 1.2 2.2 2.4 1.2 2.4 2.6 1.2 3.6 3.7 1.3 2.8 2.5 3.9 2.7 1.6 3.3 3.9 Plate thickness s 1.8 1.3 3.9 1.3 3.3 1.5 3.2 1.7 1.9 3.7 2.7 2.3 3.0 3.2 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 2.7 3.2 3.8 1.8 1.3 1.2 2.9 2.2 2.2 2.4 2.7 3.8 1.8 2.2 3.4 2.2 2.7 2.4 3.0 3.6 3.6 3.9 1.0 3.6 3.0 3.0 3.3 3.0 3.4 2.2 3.4 3.4 2.3 2.3 2.7 1.7 1.7 1.8 2.7 2.1 3.9 Plate thickness s 1.7 2.7 1.4 3.2 2.0 2.7 1.0 3.6 1.0 3.4 3.9 2.2 2.0 3.1 3.7 1.9 2.8 1.7 2.2 3.2 3.7 2.7 1.7 2.3 3.3 3.9 1.0 3.8 2.9 2.4 3.0 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 2.7 1.0 2.7 1.0 3.2 3.7 1.7 2.4 3.8 2.3 3.7 1.2 3.4 2.4 3.2 3.7 1.3 3.2 2.0 3.2 2.2 2.2 3.3 3.7 1.2 3.2 3.7 1.2 3.3 2.6 3.2 2.7 2.3 2.4 2.0 3.7 2.5 2.7 1.8 1.9 3.7 1.2 2.0 3.8 1.1 3.2 3.9 3.7 2.7 2.2 3.9 1.4 2.2 3.8 1.0 2.7 1.7 3.8 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 2.5 2.0 3.2 3.1 3.7 2.5 3.0 3.7 1.3 3.1 3.3 2.7 2.5 2.2 2.8 1.3 3.8 1.7 1.4 2.7 2.5 2.0 3.1 3.3 2.2 3.3 2.9 3.2 2.3 3.1 1.0 3.5 3.8 1.2 2.3 1.7 1.6 3.3 2.3 2.7 2.2 3.7 1.3 mm larger Internal preliminary tests should be carried out with other screws or plate materials.2 2.2 2.7 2.4 2.2 3.0 3.5 2.0 3.5 3.7 2.7 1.4 3.7 1.7 3.9 Tapping hole diameter db for thread size ST 3.2 2.1 3.4 3.4 3.2 2.0 3.7 3.7 1.4 1.3 3.1 3.0 3.7 2.2 3.1 3.9 1.5 Plate thickness s 1.4 3.4 2.4 3.2 2.9 2.7 1.2 2.7 1.2 Plate thickness s 0.2 2.9 2.7 1.9 3.0 3.3 2.6 2.2 3.5 2.2 3.7 1.8 1.0 3.3 3.2 2. Z • Tapping hole drilled • Tapping screw case-hardened and uncoated • Screwing torque ≤ 0.9 2.7 1.7 1.7 1.0 3.3 2.9 2. Reference values for the tapping hole diameter Tapping hole diameter db for thread size ST 2.4 3.8 1.0 3.7 2.9 1.8 1.2 3.2 2.0 2.4 3.9 1.8 1.2 3.3 3.2 2.0 3.2 3.2 3.3 3.7 1.0 3.4 3.8 2.7 2.2 3.8 0.6 3.3 2.2 3.6 2.1 3.7 2.2 3.6 1.0 3.2 2.8 1.6 3.9 2.4 2.7 2.5 3.5 3.2 2.2 3.7 2.2 2.4 2.2 2.7 2.3 3.4 3.2 3.7 1.9 2. 3 6.0 4.2 4.0 4.6 3.2 4.1 7.3 6.9 2.0 4.2 4.4 5.5 5.1 7.8 3.3 5.7 1.1 7.4 7.1 4.9 3.3 6.0 Plate thickness s Tapping hole diameter db for thread size ST 8 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 6.0 3.6 3.2 5.7 4.8 4.6 3.0 3.4 4.2 4.6 4.9 4.8 4.0 2.4 7.5 4.5 4.4 7.7 5.1 7.0 5.6 5.9 4.2 4.9 7.0 4.1 7.8 7.3 7.1 4.2 5.2 4.0 4.8 1.9 4.0 5.2 5.5 4.1 3.6 4.1 5.4 4.6 4.4 4.1 4.9 4.3 5.3 6.2 3.9 4.2 2.5 6.7 5.7 4.6 5.7 4.0 7.7 5.8 4.3 6.9 4.7 4.8 5.5 6.2 5.2 7.8 5.0 2.9 4.9 5.6 4.7 4.6 3.5 6.6 3.7 6.2 3.1 7.1 7.9 5.3 5.2 4.0 5.6 6.0 4.6 3.7 3.3 6.2 7.3 6.7 4.4 6.7 4.4 7.3 7.9 4.7 5.9 4.9 4.2 7.6 3.4 5.8 3.6 3.8 1.8 3.9 4.5 5.4 5.1 2.8 3.1 5.0 5.0 4.5 4.4 7.2 7.3 6.5 5.5 4.3 5.8 4.6 4.0 5.7 3.2 4.6 1.4 7.3 Plate thickness s 1.9 4.8 4.6 4.3 6.8 6.8 5.5 5.9 4.9 3.5 2.1 4.0 7.1 4.6 3.8 3.8 4.Tapping hole diameter db for thread size ST 4.9 7.7 5.9 7.2 4.2 4.5 Plate thickness s 1.8 6.8 1.2 4.1 4.9 3.5 5.7 6.2 5.6 4.7 4.8 5.5 6.5 5.9 5.7 5.2 4.8 5.2 4.1 4.1 4.3 7.9 2.6 3.3 2.6 3.6 6.9 4.5 5.0 5.8 7.8 7.8 4.0 7.7 3.3 7.9 4.2 4.8 1823 10 .2 5.3 7.5 5.2 4.2 4.5 2.2 7.9 4.4 5.9 3.8 5.6 3.4 7.3 7.7 6.1 4.1 7.7 4.4 6.0 7.4 5.2 4.3 7.8 6.0 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 3.0 4.4 5.4 4.2 5.7 5.7 5.3 6.1 7.1 4.3 3.0 4.6 3.3 5.0 5.4 7.5 4.2 4.3 7.8 5.2 4.6 5.8 5.5 4.0 4.2 4.3 5.9 5.8 4.8 3.9 4.3 4.4 5.2 3.0 4.8 3.1 7.3 7.0 4.9 4.8 5.3 7.6 4.9 4.3 4.9 3.4 6.4 7.8 3.4 5.0 3.9 4.9 7.3 7.9 7.5 Tapping hole diameter db for thread size ST 5.0 4.6 4.8 5.5 5.0 7.5 4.6 5.3 7.0 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 4.8 6.0 4.2 2.8 4.7 4.0 4.6 3.6 5.4 4.6 3.4 6.0 4.3 5.4 4.2 4.7 5.2 4.9 2.0 4.2 3.2 4.5 2.8 5.3 7.6 4.2 7.3 6.7 5.8 5.4 6.0 4.9 5.9 4.7 5.3 5.3 3.4 7.8 3.9 4.4 Tapping hole diameter db for thread size ST 6.6 5.6 3.5 Material strength Rm N/mm2 100 150 200 250 300 350 400 450 500 4.2 4.0 3.9 4.9 4.8 4.0 6.7 3.2 4.2 4.9 5.6 3.5 4.2 7.7 6.5 6.9 4.4 7.9 4.0 7.6 5.9 4.3 7.2 7.2 7.2 2.7 5.0 7.8 6.2 6.6 3.9 4.6 3.8 3.7 4.2 4.3 6.2 4.6 3.6 3.6 3.3 7.2 2.6 5.9 4.4 5.7 5.5 4.5 2.7 4.8 4.4 7.7 5.8 3.9 4.7 3.8 4.3 7.2 7.8 4.6 3.3 7.6 4.8 4.0 4.5 5.3 7.4 7.6 5.0 2.2 7.6 4.3 4.2 4.4 6.6 5.4 5.2 4.8 Plate thickness s 1.9 7.8 5.1 7.7 3.2 4.9 5.1 4.8 5.7 4.4 4.3 6.7 5.0 4.8 4.5 5.4 6.0 3.1 7.2 7.5 5.7 4.9 4. 4 1.5 4.5 0.1 3.15 8 4.2 1.1 1.41 2.6 1.76 2.5 2.55 4.84 2.90 2. min.9 1.85 7.90 1.26 0.52 1.6 0.70 4.51 0.63 1.1 1.90 1.88 0.34 0.2 20 ≈ max.3 1.91 3.15 6 3.35 2.86 3.2 0.03 4.9 2. Style C Style F 10 1824 . min. max.68 0.80 1.6 2.3 1.5 2.44 7.6 12 ST 2.6 1. min.1 0 ST 3.17 3.5.3.1 9.60 0.17 1.51 2.64 0.3 3.73 2.84 0.5 1.52 1.1 8 7.2 1 ST 4.3 1.67 2.15 6.20 5.8 3 ST 5.53 3.99 3.95 2.3 3.65 9.6 2 ST 4.38 0.3 3.9 1. min.8 4.3 3.69 0.21 2.1 3.73 1.4 4.24 1.5 1.25 6.64 2.46 5.7 2.5 6 ST 9.47 1.02 0. max.76 1.43 7.43 1.08 0. min.62 3.58 3.10 2. min.6 14 ST 3.99 5.22 4. dimension Number Thread size P d1 d2 d3 c y Aux.1 3.9.9 0.7 7 ST 1.5 1.12 0.18 2.5 to ST 9.8 1.78 6.8 8 ST 2.8 6. Style C Style F ≈ max.01 1.08 2.37 0.79 0.39 2.88 4.12 2. max.30 3.1 2 1.15 5 3.1 4 ST 6.2 2.12 1.91 0.8 5.92 2.1 2. Thread size P d1 d2 d3 c y Aux.69 0.2 Thread for tapping screws The dimensions for tapping screws such as pitch and diameter are shown in table 48 for ST 1.2 16 ST 3.30 3.6 4.1 2.29 2.24 0.57 2.28 4.43 3.24 2.59 7. dimension Number ST 1.8 2.15 4.04 3.2 10 ST 2.1 3 2. max.84 5.77 2.1 2.1 1. max.5 5 ST 8 2. max. DIN 124 (from 10 mm)). The end faces are only slightly flared to secure the pins from falling out. This type of rivet is frequently used to join metal parts with sensitive materials (leather. However. 10.1.10.1 Solid rivets Solid rivets are used less and less. which is still used occasionally in steel constructions. Rivet pins are simple cylindrical steel pins who’s end face is either countersunk to 120° or has a short bore hole. round head Countersunk head Blind rivet. 7340 (made from tube)) are cylindrical sleeves that have a flat edge at one end. For this reason only a load causing shear stress is permissible.1 Rivet types 10. riveting is being replaced here as well by joining with HV fasteners. The most common head form is the round head rivet (DIN 660 (to 8 mm). plastics) in electrical engineering and in the 1825 Raised countersunk head 10 . rubber (no tearing). cardboard. RIVETING 10.2 Hollow rivets In contrast to solid rivets. treads and catwalks where the surface has to be non-slip and safe to walk on without risk of an accident. They have been replaced in many cases by welding or bonding. Blind rivet. hollow rivets are still in demand. A special tool is used to flange the other end during processing. felt. Round head rivet Countersunk head rivets (DIN 661 (to 8 mm). the connection can only support lower loads.1.1. countersunk head Oval head rivets (DIN 662) are still used in many cases for stairs. Because of the large countersinking angle of 140° flat countersunk head rivets (DIN 675) are very often used to join soft materials such as leather. DIN 302 (from 10 mm)) are used wherever the rivet head must not project.3 Tubular rivets Tubular rivets (DIN 7339 (made from strip). Over the last ten years blind rivets above all have experienced an enormous boom because they are relatively easy to work with. However. Countersunk head rivet 10. i. Style B rivet part closed 10. Rivet part Head Style A. Same uses as for rivet pins. The rivet consists of the rivet sleeve and a mandrel. This creates a firm riveted connection with good properties against vibrations. rivet part open Hollow rivet. one-piece 10.7 Blind rivets This type of rivet has gained greatly in importance. In addition.toy industry.1.6 Two-piece hollow rivet This type of rivet is used very frequently for subordinate purposes. In place Rivet part Head Expanding rivet 10.5 Semi-tubular pan head rivets This rivet type (DIN 6791 and DIN 6792) is characterised by the fact that only the rivet end has to be processed. it is fitted blind. It is differentiated in accordance with the type of the rivet part: 10 1826 . the great advantage is that the rivet can be inserted from one side. Two types are differentiated as follows: closed blind rivets (cup-type blind rivets) are suitable for making splash-proof connections.4 Expanding rivets Expanding rivets (hammer drive rivets).e. A hammer is used to drive a pressed slotted pin or a grooved expanding mandrel into the hollow part.1.1. A further advantage of these tubular rivets: cables can be led through the very clean hollow part. Round head Semi-tubular pan head rivet 10. in particular for joining thin-walled plates or in hollow profile construction. No special tools are required for these rivets.1. Blind rivet.3 Definitions and mechanical parameters Blind rivet. open (standard type) min. dk Head diameter FZ Tensile force affecting the sleeve FQ Shearing force affecting the sleeve Splice plate joint ✘ ✔ Soft claw blind rivets. closed (cup-type blind rivet) 10.1 Joining hard to soft materials Soft and hard parts are often fastened with the help of an additional washer at the sleeve head that is pressed against the soft material.2. A much better method is to use a rivet with a large mushroom head and to place the sleeve head against the hard material.2. all-purpose rivets (press clip rivets) are recommended for this application. 2 x d d 10.2 Corner clearances for connections: To enable the greatest possible joint strength. the clearance from the centre axis of the rivet to the edge of the workpiece should not be less than twice the diameter of the sleeve. 1827 10 .2 Instructions for use 10.10. blind rivets with a grooved rivet shaft. (Fig. while the remainder of the mandrel in the rivet sleeve is sealed tight by the rivet sleeve. 1) Fig. The mandrel breaks off at the predefined rupture joint. 10 1828 . (Fig. 3) d 1 d 3 dk l Id k Sleeve diameter Mandrel diameter Head diameter Sleeve length Mandrel length Head height 10. The very universal range is for material thicknesses of 0. 3 10. because they can only be set from one side (blind assembly). 2) The rivet connection is complete and does not require any more step to finish.5 mm. 1 The pulling movement causes the rivet head to deform the sleeve and this leads the two workpieces to be pressed firmly together.5–7.Fig.4 Using blind rivets The rivet is placed with the rivet mandrel into the opening of the rivet tool and into the bore hole with the rivet sleeve. (Fig. flat head Rivet nuts combine two fastening types: blind riveting and an additional screw assembly. Fig. 2) Blind rivet nut. the clamping jaws grip the mandrel and pull it back. When the tool is operated.5 Rivet nuts These nuts are mainly used with hollow bodies. 2 The sleeve is pressed against the hole wall inside the material bore hole and at the same time is shaped from the “blind” side to the closing head. (Fig. agricultural engineering 10. The rivet screw is screwed into the threaded sleeve of the rivet tool and the rivet sleeve is then inserted into the prepared bore hole. electrically insulating rivet connection with oscillation and noise-restricting function for fastening metal and plastic connections.5. Hardness: 60 Shore. Areas of application: Electronics construction.5. The pulling movement causes the rivet head to deform the sleeve and this leads the two workpieces to be pressed firmly together. trailer construction. Possible operating temperatures: –30°C to +80°C. The nut is then placed into the prepared bore hole. When the tool is operated the threaded mandrel is withdrawn. Method of use Design: mushroom head. The blind rivet nut is screwed onto the threaded mandrel of the rivet tool.10. Advantages: can be used in blind or pocket holes. 1829 10 . The pulling movement causes the threaded mandrel to deform the sleeve and this leads the two workpieces to be pressed firmly together.6 Rivet screws Rivet screws are used analogously to rivet nuts.2 Special types of rivet nuts Neoprene rivet nuts Detachable. When the tool is operated the threaded sleeve is withdrawn. plant engineering. vehicle construction. Blind rivet nut. Ozone-resistant. countersunk head This makes it possible above all to use screw assemblies in relatively thin-walled construction elements. Double function as thread carrier or fastener. sign making. Ideal for various materials. Material: rivet body made of neoprene (EPDM) with brass insert.1 Using rivet nuts The blind rivet nuts are used in a similar way to blind rivets. 10. air-conditioning and refrigeration engineering. Air-tight and moisture-proof connection. 7.3 Multi-range blind rivet: Blind rivet that unites several grip ranges in a single rivet (grip range to 20 mm possible). Its blind rivet sleeve is connected to the head in the shape of a cup and in com parison with open blind rivets is proof against splashed water. Spin the screw off 6. Screw into the appliance opening 3. The grip range of the components is the total of all components that are to be connected.2 Grip range: The range in which a blind rivet with a given rivet sleeve length fulfils its riveting task perfectly. Other assembly faults can occur through the choice of the incorrect grip or riveting tool.8.7.1 Selected grip range too large: • The mandrel does not break off at the rupture joint so that it may still project from the drawn sleeve after processing.8.4 Rivet sleeve diameter: The external diameter of the rivet sleeve. Riveting several plates together with an additional screwedon component Procedure for use 10.3 Bore hole too big: • The rivet can be inserted but there is no high connection strength because the sleeve material is insufficient to fill the bore hole. 10. 10. 10. 10. • The connection has insufficient or no tensile or shearing strengths.7 Trouble shooting 10. Frequently also referred to as well as the shaft diameter. Rivet together by tightening the screw 5.2 Grip range too small: • The connection has weak points in the area of tensile and shearing strength. 10.5 Rivet sleeve length: With blind rivets with mushroom heads the rivet sleeve length is measured to the start of the mushroom head.This type of connection results in a high-strength screw thread in thin-walled materials. 10. 10.8 Explanation of terms 10. Blind rivet screw 2.4 Bore hole too small: • The rivet sleeve cannot be inserted into the material because the rivet sleeve diameter is greater than the bore hole.8.7. With the countersunk head design the rivet sleeve length is the total length including the countersunk head and the sleeve. • The rivet mandrel breaks off at the rupture joint but still projects from the sleeve. 10 1830 .8.8.1 Cup-type blind rivet: Also known as sealed rivet.7. 10.6 Closing head: The part of the blind rivet sleeve that is shaped by the head of the rivet mandrel after setting. Insert into the workpiece’s bore hole 4. 1. 10.8. Designed as a round or countersunk head.8. 1831 10 .10.8.8 Rupture joint: Mandrels have notches at which they break off on the maximum deformation of the rivet sleeve.7 Setting head: The factory-shaped head at the blind rivet sleeve that is not deformed. 10. 10 1832 .