Global Dimensioning And Tolerancing Addendum (GD&T) – 2004

ENGINEERING STANDARDSDesign Standard Electronic C2B Global Dimensioning And Tolerancing Addendum – 2004 Contents Foreword…………………………………..2 GM Acknowledgement…………………....2 Automotive Industry Representative Acknowledgment……………...…………..2 Structure………………………………..….2 General Motors Authorization…………….2 Figures…………………………………….3 Titleblock Notes…………..…………….…3 Section 1 Scope, Definitions, and General Dimensioning 1.3 Definitions……………………………..4 1.4 Fundamental Rules…………………….7 1.5 Units of Measurement…………………8 1.6 Application of Dimensions……………8 1.7 Dimensioning Features………………..8 1.8 Location of Features……………….….9 Section 2 General Tolerancing and Related Principles 2.7 Limits of Size…………………..…….25 2.8 Applicability of RFS, MMC, and LMC………………………………..…….26 2.15 Radius………………………………27 2.16 Statistical Tolerancing……..……….27 2.17 Uniform Thickness/Gap Tolerance…………………………………27 Section 3 Symbology 3.3 Symbol Construction………………...32 3.5 Feature Control Frame Placement…...32 Section 4 Datum Referencing 4.2 Immobilization of Part………..……...35 4.4 Specifying Datum Features in an Order of Precedence………...…….……...35 4.5 Establishing Datums…………………35 4.6 Datum Targets………………………..37 4.7 Restraining Datum Features………….37 4.8 Restraining Conditions…………….…38 Section 5 Tolerances of Location 5.3 Fundamental Explanation of Positional Tolerancing………………………………50 5.11 Coaxiality Controls…………………51 5.12 Concentricity………………………..51 5.14 Symmetry Tolerancing……………...51 5.16 Cylindrical Part with Bends………...51 Section 6 Tolerances of Form, Profile, Orientation, and Runout 6.5 Profile Control……………………….53 6.6 Orientation Tolerances……………….54 6.8 Free State Variation………………….54 APPENDIX B Formulas for Positional Tolerancing B1 General……………………………….57 Appendix New F Effect of Changes to the Definition of Actual Mating Envelope on the Figures in Y14.5 F1 General………………………………..57 © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Originating Department: North American Engineering Standards Page 1 of 59 C2B Foreword General Motors Corporation and Delphi Corporation have adopted an amended version of the ASME Y14.5M-1994 dimensioning and tolerancing standard (amended by this addendum) for use by the above companies on all product engineering documentation. This addendum was created to address the following areas: 1. Select an option from ASME Y14.5 2. Clarify a concept from ASME Y14.5 3. Discourage/disallow the use of a concept from ASME Y14.5 4. Include a concept not covered by ASME Y14.5 All other standards referenced in ASME Y14.5 have not necessarily been adopted by the above companies, and are not automatically invoked. Current company standards will take precedence unless otherwise noted. GM Acknowledgment This document represents the consensus of the members of the GM GD&T Task Team. GM GD&T contributing members: Michael A. Murphy, GMPT Robert Bourland, GMPT Guy Browne, Holden Thomas Drexler, Opel Anders Gustavsson, Saab James Gyomber, Holden Gisela Herzing, GM Ruesselsheim Alex Krulikowski, GMPT Dale MacPherson, GMPT Cliff McCord, NAVO Tibor Nuebl, Opel Hans-Olof Svensson, Saab Susan Belloli, GMPT Klaus W. Schulz, Opel Powertrain GmbH Andy Watts, NAVO Duane Harbowy, GMPT GM ENGINEERING STANDARDS Automotive Industry Representative Acknowledgment This addendum also represents input of the following automotive industry representatives: Neil Freson, Delphi Energy & Chassis Systems Paul Sams, Delphi Delco Electronics Systems Dave Arnold, Delphi Safety & Interior Systems James Anderson, Delphi Harrison Thermal Systems Bruce Eggert, Delphi Harrison Thermal Systems Dan Meyers, Delphi Delco Electronics Systems Jamie Florence, Aerotec (figure construction) General Motors Authorization This standard is authorized by the GM Global Engineering Design Committee Notice of Action # GEDC 162. Structure The paragraph numbering in this addendum is as follows: Paragraphs are generally numbered to coincide with numbers in ASME Y14.5. Paragraph numbers preceded by “NEW” are additions to Y14.5. Unless otherwise noted, paragraphs not preceded by “NEW” replace the paragraph in Y14.5 that is identified by the same number. Italicized text may be added, following the paragraph title noting whether the paragraph is a deletion or to describe the changes to an existing paragraph in Y14.5. Paragraph references noted in the figures refer to the paragraphs contained in this document. Figures referenced in the text but not shown in this addendum are found in Y14.5. Paragraph titles contained in parenthesis are for index referencing only and do not reflect changes to Y14.5. The words “shall/must/required” describe strict requirements. Procedural steps defined by these words must be followed. The words “should/preferred/recommended” describe preferences. Procedural steps defined by these words must be followed whenever there is no valid reason to do otherwise. The words “acceptable/allowed/may/might” grant permission. They do not require or recommend the practice they specify; neither do they forbid or discourage alternative practices. © Copyright 2004 General Motors Corporation All Rights Reserved Page 2 of 59 October 2004 GM ENGINEERING STANDARDS Figures The figures in this Addendum exhibit the arrow method of view projection. GM Engineering Standards – Drawing Views and Sections (C3) Titleblock Notes The note shown in Fig. F-1 shall appear on drawings, documents or within databases which are in accordance with the General Motors Global Dimensioning and Tolerancing Addendum – 2004. The note shall be in the title block (or in the general notes). The note invokes this addendum. THIS DOCUMENT IS IN ACCORDANCE WITH ASME Y14.5M-1994 AS AMENDED BY THE GM GLOBAL DIMENSIONING AND TOLERANCING ADDENDUM – 2004. Figure F-1 – Note To Invoke Gm Global Dimensioning And Tolerancing Addendum – 2004 C2B © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 3 of 59 C2B 1 Scope, Definitions, and General Dimensioning 1.3 Definitions. 1.3.3 Datum. A theoretically exact point, axis, line, or plane derived from the true geometric counterpart. A datum is the origin from which the location or geometric characteristics of features of a part are established. 1.3.5 Datum Feature Simulator. A surface of adequately precise form (such as a surface plate, a gage surface, fixture pad, pin, centering device, or a mandrel) used to establish the simulated datum(s). Note: Datum feature simulators are used as the practical embodiment of the datums during manufacture and inspection. 1.3.7 Datum Target. A specified point, line, or area on a drawing that represents a theoretically perfect fixture element. 1.3.9 Dimension, Basic. A numerical value used to describe the theoretically exact size, profile, orientation, or location of a feature; orientation or location of feature of size; or datum target. See Fig. 3-7. It is the basis from which permissible variations are established by tolerances on other dimensions, in notes, or in feature control frames. See Figs. 2-14, 2-15, and 325. Title block or general plus/minus tolerances do not apply to basic dimensions. 1.3.11 Envelope, Actual Mating. A general term used to refer to an unrelated or related actual mating envelope. Note: Changes to the definition of Actual Mating Envelope have had numerous effects on figures in Y14.5. Appendix NEW F outlines the effects on figures in Y14.5. 1.3.11.1 Envelope, Unrelated Actual Mating. An unrelated actual mating envelope, (unrelated to a datum reference frame), can be either external or internal as described below: (a) For an external feature of size, a similar perfect feature counterpart of smallest size that can be circumscribed about the feature of size so that it contacts the surface or surfaces. For example, a smallest cylinder of perfect form or two parallel planes of perfect form at minimum separation that contacts the surface(s). See Fig. 1-57. (b) For an internal feature of size, a similar perfect feature counterpart of largest size that can GM ENGINEERING STANDARDS be inscribed within the feature of size so that it contacts the surface or surfaces. For example, a largest cylinder of perfect form or two parallel planes of perfect form at maximum separation that contacts the surface(s). 1.3.11.2 Envelope, Related Actual Mating. A related actual mating envelope, (related to a datum reference frame), can be either external or internal as described below: (a) For an external feature of size datum feature, a similar perfect feature counterpart of smallest size that can be circumscribed about the feature of size so that it contacts the surface or surfaces. For example, the smallest cylinder of perfect form or two parallel planes of perfect form at minimum separation that contacts the surface(s). This envelope is oriented relative to the appropriate datum(s), See Fig. 1-57. (b) For an internal feature of size datum feature, a similar perfect feature counterpart of largest size that can be inscribed within the feature of size so that it contacts the surface or surfaces. For example, the largest cylinder of perfect form or two parallel planes of perfect form at maximum separation that contacts the surface(s). This envelope is oriented relative to the appropriate datum(s). 1.3.12.1 Feature, Interrupted. A feature, (surface), that has an interruption. The keyword INTERRUPTED is placed adjacent to a size dimension, feature control frame or the datum feature symbol indicating that the specified tolerance zone, size dimension or datum feature applies through the interruption. See fig. 1-59. 1.3.13 Feature of Size, Axis Of. A straight line that coincides with the axis of the unrelated actual mating envelope of a feature of size. See Fig. 1-57. 1.3.14 Feature of Size, Center Plane Of. A plane that coincides with the center plane of the unrelated actual mating envelope of a feature of size. 1.3.15 Feature of Size, Derived Median Plane Of. An imperfect plane (abstract) that passes through the center points of all line segments bounded by the feature of size. These line segments are normal to the unrelated actual mating envelope. 1.3.16 Feature of Size, Derived Median Line Of. An imperfect line (abstract) that passes through the center points of all cross sections of the feature of size. These cross sections are October 2004 © Copyright 2004 General Motors Corporation All Rights Reserved Page 4 of 59 GM ENGINEERING STANDARDS normal to the axis of the unrelated actual mating envelope. The cross section center points are determined as per ANSI B89.3.1. 1.3.17 Feature of Size. A general term used to refer to a whole or interrupted feature of size. 1.3.17.1 Whole Feature of Size. A single cylindrical or spherical surface, or circular element, or a pair of parallel surfaces or elements, that may be truncated or have an obstruction or recess that satisfies one of the following conditions: (a) A circular element associated with a diametral limit or plus and minus dimension that may have one or more obstructions or recesses. Any obstruction or recess must be less than 180 degrees of rotation around the axis. See Fig. 170 (b) A cylindrical surface associated with a diametral limit or plus and minus dimension that may be truncated or have one or more obstructions or recesses, (for example: drilled holes, keyway, partial spline shaft, partial thread, partial groove, partial bead, etc.),. Any obstruction or recess must be less than 180 degrees of rotation around the axis. See Figs. 1-62 and 1-63. (c) A spherical surface associated with a diametral limit or plus and minus dimension that may have one or more obstructions or recesses, (for example: drilled holes, partial groove, partial bead, etc.),. Any obstruction or recess must be less than a hemisphere. See Fig. 1-71 (d) A helical surface associated with a diametral limit or plus and minus dimension, such as a major diameter of an external thread or minor diameter of an internal thread,. See Fig. 1-72 (e) A set of two opposed point elements associated with a limit or plus and minus dimension. The associated dimension defines the variation of the length of a line segment terminating at the point elements. See Fig. 1-58(a). (f) An opposed point and line element, associated with a limit or plus and minus dimension. The associated dimension defines the variation of the length of a line segment terminating at the point and line elements, and normal to the line element. See Fig. 1-58(b). (g) An opposed point and a planar surface that may have an obstruction or recess, (for example: drilled holes, partial groove, partial bead, etc.), associated with a limit or plus and minus dimension. The associated dimension defines October 2004 C2B the variation of the length of a line segment terminating at the point element and planar surface, and normal to the planar surface. See Fig. 158(c). (h) A set of two opposed parallel line elements, associated with a common limit or plus and minus dimension. The associated dimension defines the variation of the length of a line segment terminating at, and normal to the opposed line elements. See Figs. 1-66, 1-67(b) and 1-58(d). (i) An opposed parallel line element and planar surface associated with a common limit or plus and minus dimension that may have an obstruction or recess, (for example: drilled holes, partial groove, partial bead, etc.),. The associated dimension defines the variation of the length of a line segment terminating at the line element and planar surface, and normal to the opposed elements. See Figs. 1-67(b) and 1-58(e). (j) A set of two opposed parallel surfaces associated with a common limit or plus and minus dimension, each of which may have an obstruction or recess, (for example: drilled holes, keyway, partial spline shaft, partial thread, partial groove, partial bead, etc.),. The associated dimension defines the variation of the length of any line segment terminating at, and normal to the opposed parallel surfaces. See Figs. 1-74, 1-58(f). 1.3.17.2 Feature of Size, Interrupted. A feature of size that has an interruption in one of the associated features or elements. The keyword INTERRUPTED is placed adjacent to the size dimension, tolerance or datum feature symbol indicating that the specified tolerance zone, size dimension or datum feature applies through the interruption. For circular elements and cylindrical surfaces any recess or obstruction must be less than 180 degrees of rotation around the axis. See Figs. 1-59(a) and(b), 1-60, 1-64, 1-65 and 1-74. 1.3.26.1 Size, Unrelated Actual Mating Envelope. The value of the unrelated actual mating envelope. See Fig. 1-57. 1.3.26.2 Size, Related Actual Mating Envelope. The value of the related actual mating envelope. See Fig. 1-57. 1.3.35 True Geometric Counterpart. The theoretically perfect boundary of a feature of size datum feature virtual condition for LMC or MMC applications, datum target, unrelated actual mating envelope for RFS primary datum features or © Copyright 2004 General Motors Corporation All Rights Reserved Page 5 of 59 must be in opposite directions and normal to the surfaces from which the point and line elements are derived. Also see paras. A point element A and a planar surface B are opposed if the following conditions apply: Vectors originating and extending from point A and surface B.C2B related actual mating envelope for RFS secondary or tertiary datum features or best-fit (tangent) plane for planar datum features. line. 1.16. and directed away from the material.38 Free State.41.4 Opposed Parallel Line Elements.3. A point. must be in opposite directions and normal to the surface from which the point element is derived. A and B. 1. they shall not be considered opposed elements.42 Uniform Thickness/Gap. See Fig. The surface normal vectors directed away from each surface's material side must be in opposite directions. 1-58(a). 1. must be in opposite directions and normal to the surfaces from which the point elements are derived.3.41.3. they are not considered opposed elements.43 Uniform Thickness/Gap Feature. 1. When both points lie on the same line element other than line end points. 1-58(f) and 66.41. 4-11. The GM ENGINEERING STANDARDS element and planar surface is opposed if a vector originating and extending normal from surface B intersects point A. 1. and 4-10. that are coincident to a line through point A and normal to surface B. 1. See Fig.3 regarding the simulated datum. See Fig.41 Opposed Elements. Two (2) point elements. If line element A lies on a planar surface perpendicular to surface B.1 Opposed Point Elements.3.40 Element. 1-58(e). When the point element and line element lie on the same line or both elements lie on the same planar surface.41. Line element A and planar surface B are opposed if a vector originating and extending normal from line element A intersects planar surface B. 1-58(d) and 1-66. Vectors. they shall not be considered opposed line elements. A pair of continuous surfaces or portions thereof that are nominally equidistant and associated with a Uniform Thickness/Gap tolerance. See Figs. or arc derived from a surface. 1.3.3. A and B. and directed away from the material.3.3. Two surfaces are opposed if a vector originating and extending normal from surface A intersects surface B.1 and 1. 1. When both lines lie on the same planar surface. See Figs. are opposed if the following conditions apply: Vectors originating and extending normal from lines A and B in a plane containing lines A and B. The elements are opposed if a vector originating and extending normal from line element B intersects point A. other than the surface edge.3. See Figs.2. A point element A and a line element B are opposed if the following conditions apply: Vectors originating and extending from point A and line B that are coincident to a line through point A and normal to line B. 1. and directed away from the material.3.16.3. A general term used to refer to elements as described in paragraphs 1. other than the surface edges. The condition where no forces other than gravity are applied. must be in opposite directions and normal to the surfaces from which the line elements are derived. and directed away from the material.3. A line element A and a planar surface B are opposed if the following conditions apply: Vectors originating and extending normal from line A and planar surface B in a plane containing line A and normal to surface B. 1-58(b). Two (2) line elements.3. The condition where forces in addition to gravity are applied. See Fig. Two (2) surfaces. 1. A and B. must be in opposite directions. 1.3. Two line elements are opposed if a vector originating and extending normal from line element A intersects line element B. originating and extending normal from surfaces A and B. other than the surface edges.41. are opposed if the following conditions apply: Vectors originating and extending from points A and B that are coincident to a line through points A and B.39 Restrained. and directed away from the material.41.3. © Copyright 2004 General Motors Corporation All Rights Reserved Page 6 of 59 October 2004 .3.3 Opposed Point Element and Planar Surface. 1. they shall not be considered opposed elements. and directed away from the material.5 Opposed Parallel Line Element and Planar Surface.2 and 1. must be in opposite directions.6 Opposed Parallel Surfaces. A condition where two surfaces are nominally equidistant. When the point element and planar surface lie in the same plane.2 Opposed Point and Line Element. are opposed if the following conditions apply: The two surfaces are planar. 1. 1-58(c). they shall not be considered opposed elements. The length of the element is constrained by the bounds of the part surface. or planar surface other than the surface edges. 3. (g) Dimensions should be arranged to provide required information for optimum readability. etc. 1. ALL OVER. 2. Dimensions should be shown in true profile views and refer to visible outlines. reamed. 1. minimum. A protrusion or opening that constitutes a complete break resulting in more than one distinct partial surface or element. 1-68(b). templates. See para. The use of reference dimensions on a drawing should be minimized.3. However.).GM ENGINEERING STANDARDS Note: A Uniform Thickness/Gap Feature is not a feature of size. See Fig. etc. Thus. The surface that results from a closed contiguous contour in a given plane projected along a vector normal to the plane. (e) The drawing should define a part without specifying manufacturing methods. sheets. 1. See ANSI Y14. full length of a major diameter of an external spline shaft.) 1.3.47 Recess. shaft. star pin. printed wiring.3. annular groove(s). except as follows: Undimensioned drawings. only the diameter of a hole is given without indicating whether it is to be drilled. A protrusion that violates a part surface and does not constitute an interruption. rods. processing. quality assurance. (f) It is permissible to identify as nonmandatory certain processing dimensions that provide for finish allowance.46 Obstruction.e.. (For Example. shrink allowance. (i) A 90 degree angle applies where center lines and lines depicting features are shown on a drawing at right angles and no angle is specified. The tolerance may be applied directly to the dimension (or indirectly in the case of basic dimensions). Neither scaling (measuring the size of a feature directly from an engineering drawing) nor assumption of a distance or size is permitted. hole. See Fig.50 Pattern.5M-1994): nX. punched.49 Bounded Feature. An opening that violates a part surface and does not constitute an interruption. A single surface of revolution at a constant nominal radius containing at least one circular element that nominally occupies more than 180 degrees of rotation around an axis. such as NONMANDATORY (MFG DATA). cables. (b) Dimensioning and tolerancing shall be complete so there is full understanding of the charac- C2B teristics of each feature.2.1. or stock (commercial stock size).4 Fundamental Rules. (i. in those instances where manufacturing.3. 1. Dimensioning and tolerancing shall clearly define engineering intent and shall conform to the following. or environmental information is essential to the definition of engineering requirements. Two (2) or more features or features of size to which a locational geometric tolerance is applied and are grouped by one of the following methods (per Y14. nCOAXIAL HOLES. 1. A ↔ B.3.48 Interruption. such as loft.44 Circular Element. 1-67(a).) See Fig. or located in a supplementary block of the drawing format. a) Each dimension shall have a tolerance. indicated by a general note. it shall be specified on the drawing or in a document referenced on the drawing. © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 7 of 59 . are excluded provided the necessary control dimensions are specified. and other requirements. pin. Nonmandatory processing dimensions shall be identified by an appropriate note.1. and master layouts prepared on stable material. (c) Each necessary dimension of an end product shall be shown. (j) A 90° basic angle applies where centerlines of features in a pattern or surfaces shown at right angles on the drawing are located or defined by basic dimensions and no angle is specified. Gage or code numbers may be shown in parentheses following the dimension. (h) Wires.45 Cylindrical Surface. The intersection of a surface of revolution and a planar section perpendicular to the axis of the surface of revolution that nominally occupies more than 180 degrees of rotation around the axis.3. (d) Dimensions shall be selected and arranged to suit the function and mating relationship of a part and shall not be subject to more than one interpretation. or INDICATEDα. provided the final dimensions are given on the drawing. 1. and other materials manufactured to gage or code numbers shall be specified by linear dimensions indicating the diameter or thickness. 1-68(a). nSURFACES. No more dimensions than those necessary for complete definition shall be given. 1.1. except for those dimensions specifically identified as reference. maximum. (For example: The material that remains or is removed by extruding an outline of a planar closed geometric shape in a single vector direction through material. or made by any other operation. 1-40. Note: Toleranced angles using degree/minutes/seconds as shown in Fig’s 1-1. GM ENGINEERING STANDARDS 1. © Copyright 2004 General Motors Corporation All Rights Reserved Page 8 of 59 October 2004 . The diameter of the spotfaced area is specified.9 Location Of Features. all geometric tolerances apply for full depth.7. (l) All dimensions and tolerances apply in a free state condition. 1-1. 1. a detail drawing) is not mandatory for that feature at any other level (for example.5 Repetitive Features or Dimensions. thread depth. See Fig.7 Application Of Dimensions). Where used with a basic dimension. The dimension origin symbol should be used when direct tolerancing is specified for the examples noted. Note: Direct tolerancing methods may be used for Uniform thickness/gap. 1-73. (m) Unless otherwise specified.9(b) of ASME Y14. 1.4 Angular Units. See Fig. 1.13 Spotfaces.8 Dimensioning Features.2 shall not be used to locate features or features of size. Compensation may be made for measurements made at other temperatures. (o) Unless otherwise specified all dimensions apply after heat treat and surface treatment. This principle does not apply to nonrigid parts as defined in paras.8. (q) A zero basic dimension applies where axes.5 shall not be used. Repetitive features or dimensions may be specified by the use of an X in conjunction with a numeral to indicate the “number of places” required. an assembly drawing). with its arrowheads. length. (n) Dimensions and tolerances apply only at the drawing level where they are specified. The following shall not be used as a dimension line: a center line. (r) Direct tolerancing methods as described in paragraph 2. 1. A dimension line. 21. Either the depth or the remaining material shall be specified.C2B (k) Unless otherwise specified.7. a phantom line. and 2-13 shall not be used. size and depth of counterbores. size of chamfers. See Fig.2 shall not be used to orient features of size. Angle tolerance as described in paragraph 2. 1.3(b) and 6. Angular dimensions are expressed in degrees and decimal parts of a degree. Numerals indicate the number of units of a measurement. and width of the feature. 2.9 Dimensions Not to Scale. Dimension lines shall be broken for the insertion of numerals as shown in Fig’s 1-2 and 1-4. shows the direction and extent of a dimension.9. 1.1.3. 2-2. or a continuation of any of these lines.7. 1. size and depth of spotfaces. A dimension specified for a given feature on one level of drawing. the X shall be placed outside the basic dimension frame.5. size of corner radii. center planes or surfaces are shown congruent on a drawing.7.5 Units of Measurement. size and depth of countersinks. and surface intersections. (for example. 1. . an extension line.1 Dimension Lines. all dimensions are applicable at 20°C (68°F). a line that is part of the outline of the object. Paragraph 1. A dimension line is not used as an extension line. GM ENGINEERING STANDARDS C2B Figure 1-57 – Related And Unrelated Actual Mating Envelope © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 9 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-58 – Definition Of Opposed And Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 10 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 1-59 – Interrupted Cylindrical Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 11 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-60 Interrupted Opposed Parallel Surfaces Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 12 of 59 October 2004 . GM ENGINEERING STANDARDS Figure 1-61 – Opposed Line Elements Feature of Size DATUM C2B © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 13 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-62 – Cylindrical Whole Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 14 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 1-63 – Cylindrical Whole Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 15 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-64 – Circular Element Interrupted Feature Of Size Figure 1-65 – Circular Element Interrupted Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 16 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 1-66 – Features Of Size – Opposed Parallel Line Elements And Opposed Parallel Surfaces © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 17 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-67 – Bounded Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 18 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 1-68 – Recess And Obstruction © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 19 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-69 .Interrupted Feature © Copyright 2004 General Motors Corporation All Rights Reserved Page 20 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 1-70 .Whole Circular Element Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 21 of 59 . C2B GM ENGINEERING STANDARDS Figure 1-71 Whole Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 22 of 59 October 2004 . Whole Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 23 of 59 .GM ENGINEERING STANDARDS C2B Figure 1-72 . C2B GM ENGINEERING STANDARDS Figure 1-73 – Direct Tolerancing © Copyright 2004 General Motors Corporation All Rights Reserved Page 24 of 59 October 2004 . variations in form are constrained by the MMC virtual condition of the specified orientation tolerance. and no geometric form tolerance is specified. The form of an individual feature of size is controlled to the extent prescribed in the following paragraphs. Variation in form is allowed provided the feature of size does not extend beyond a boundary of perfect form at MMC. These criteria apply solely to individual features of size as defined in Para.3. 1. Variation in form is allowed © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 . as well as size are allowed. (c) Where a geometric tolerance of orientation is applied to a feature of size at maximum material condition and no geometric form tolerance is specified. 2. as well as size. (b) Where a geometric tolerance is applied to a feature of size regardless of feature size. orientation.GM ENGINEERING STANDARDS C2B Figure 1-74 – Interrupted Opposed Parallel Surfaces Feature Of Size provided the feature of size does not extend beyond a boundary of perfect form at MMC. no geometric tolerance of form.7. Where only a geometric tolerance of position is applied at maximum material condition.11 of this addendum. (i. the limits of size of the individual feature of size prescribe the extent to which variations in its geometric form. variations in form are constrained by the MMC virtual condition of the specified posiPage 25 of 59 2 General Tolerancing and Related Principles 2. The following paragraphs define the criteria for the specified limits of a feature of size.e.1 Individual Feature of Size. the limits of size of the individual feature of size prescribe the extent to which variations in its geometric form.. (a) Where only a tolerance of size is specified. or position is specified).7 Limits Of Size. are allowed. 6. (b) Specify a zero positional tolerance at MMC. or symmetrical to each other must be controlled for location or orientation to avoid incomplete drawing requirements. the following methods are used.7.1. If it is necessary to establish a boundary of perfect form at MMC to control the relationship between features.6. The limits of size do not control the orientation or location relationship between individual features. Paragraph 2. © Copyright 2004 General Motors Corporation All Rights Reserved Page 26 of 59 October 2004 . variations in form are constrained by the LMC virtual condition of the specified orientation tolerance.C2B tion tolerance. Note: When a feature of size contains a truncation. See paras. portions of the part surface have no opposing elements and the actual local size cannot be found.2 of ASME Y14.1. 2.11. Variation in form is allowed provided the feature of size does not extend beyond the MMC virtual condition of the applicable orientation or position tolerance.2. Where non-opposed elements exist in a feature of size. the size and form of the surface must be within the maximum and minimum boundaries established by paragraph 2. These controls may be specified by one of the methods given in Sections 5 and 6.1. Features shown perpendicular.1. Where only a geometric tolerance of position is applied at least material condition. Variation in form is allowed provided the feature of size does not extend beyond the LMC virtual condition of the applicable orientation or position tolerance.5 shall not be used.2. 5.1. recess or interruption.7. to control angularity.13.7. 2. obstruction. perpendicularity. (d) Where a geometric tolerance of orientation is applied to a feature of size at least material condition and no geometric form tolerance is specified.1.3 Relationship Between Individual Features. variations in form are constrained by the LMC virtual condition of the specified position tolerance. 2.1. or parallelism of the feature.2 Variations of Form (Envelope Principle). See para. (a) Specify a zero tolerance of orientation at MMC.3 and 5. including a datum reference (at MMC if applica- GM ENGINEERING STANDARDS ble) to control coaxial or symmetrical features. including a datum reference (at MMC if applicable). coaxial.7.1 Variations of Size. The actual local size of an individual whole feature of size at each cross section shall be within the specified tolerance of size except where a feature of size is truncated or has an obstruction or recess. and 6-42. the allowable tolerance is dependent on the unrelated actual mating size of the considered feature of size. and LMC: (a) All Applicable Geometric Tolerances (Rule #2).8. The total permissible variation in position or ori© Copyright 2004 General Motors Corporation All Rights Reserved C2B entation is maximum when the feature is at LMC. Where a tolerance of position or orientation is applied on a zero tolerance at LMC basis. rather than the axis and center plane that are controlled. the tolerance is totally dependent on the unrelated actual mating size of the considered feature. MMC or LMC must be specified on the drawing where it is required. Where the unrelated actual mating size of the considered feature has departed from MMC. an increase in the tolerance is allowed equal to the amount of such departure. a tolerance is allowed equal to the amount of such departure. it is the derived median line and the derived median plane.8. and LMC is limited to features subject to variations in size. Applicability of RFS. No tolerance of position or orientation is allowed if the feature is produced at its MMC limit of size. See Figs. 5-14. No tolerance of position or orientation is allowed if the feature is produced at its LMC limit of size where the unrelated actual mating size of the considered feature has departed from LMC. Note: Circular runout and total runout.2 Effect of MMC. referencing a datum feature of size on an LMC basis means the datum is the axis or center plane of the feature of size at the LMC limit.GM ENGINEERING STANDARDS 2. referencing a datum feature of size on an MMC basis means the datum is the axis or center plane of the feature of size at the MMC limit or virtual condition. an increase in the tolerance is allowed equal to the amount of such departure. are applicable only on an RFS basis and cannot be modified to MMC or LMC. Where the unrelated actual mating size of a primary datum feature of size.3. MMC. where no modifying symbol is specified. 6.4.8 Applicability of RFS. a deviation is allowed between its axis or center plane and the axis or center plane of the datum. The total permissible variation in position is maximum when the feature of size is at MMC. Where a geometric tolerance is applied on an MMC basis. The tolerance is limited to the specified value if the feature of size is produced at its LMC limit of size. the tolerance is totally dependent on the size of the considered feature. or the related actual mating size of a secondary or tertiary datum feature of size has departed from LMC. 2. October 2004 Page 27 of 59 . MMC.1.1. 5-13. 2. RFS applies. In all cases.1. Where the related actual mating size of the feature of size has departed from LMC.3 Effect of Zero Tolerance at MMC. The total permissible variation in the specific geometric characteristic is maximum when the unrelated actual mating envelope of the feature of size is equal to LMC value.8. See Figs. Likewise.8. unless a maximum is specified. Where the unrelated actual mating size of the feature of size has departed from MMC. the following practices apply for indicating RFS. In the case of straightness covered in paras. or both. They may be datum features or other features whose axes or center planes are controlled by geometric tolerances. Where a tolerance of position or orientation is applied on a zero tolerance at MMC basis. with respect to the individual tolerance. Where a positional tolerance is applied on an LMC basis. a deviation is allowed between its axis or center plane and the axis or center plane of the datum. The total permissible variation in position or orientation is maximum when the feature is at MMC unless a maximum is specified.4.1. The tolerance is limited to the specified value if the feature of size is produced at MMC. the allowable tolerance is dependent on the related actual mating size of the considered feature of size.2 and 6. and LMC). 2.4 Effect of LMC. Where the unrelated actual mating size of a primary datum feature of size. a tolerance is allowed equal to the amount of such departure. MMC. or the related actual mating size of a secondary or tertiary datum feature of size has departed from MMC value.5 Effect of Zero Tolerance at LMC. 6-41 and 6-42. 2. datum reference. Likewise. the surface finish requirements of the applicable radius must be noted. the part contour within the crescent-shaped tolerance zone must be a fair curve without reversals. radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit. 2.16 Statistical Tolerancing.2 Controlled Radius Tolerance.15 Radius. When specifying a controlled radius. (b) For a uniform gap feature (internal). Statistical tolerancing as described in Para. 2. 2-25 and 2-26.16 and associated sub-paragraphs of ASME Y14. 2-19. A Uniform Thickness/Gap tolerance specifies that the minimum and maximum actual Thickness/Gap value. the maximum actual thickness value is the minimum separation between two points a fixed distance apart that the entire uniform thickness feature will pass through. See Fig. 2. © Copyright 2004 General Motors Corporation All Rights Reserved Page 28 of 59 October 2004 . must be GM ENGINEERING STANDARDS within the specified Uniform Thickness/Gap tolerance limits. Additionally. The minimum actual thickness value is the minimum distance between the surfaces of a uniform thickness feature.C2B 2. as defined in (a) and (b) below. The maximum actual gap value is the maximum distance between the surfaces of a uniform gap feature. 2. the minimum actual gap value is the maximum separation between two points a fixed distance apart that the entire uniform gap feature will pass over.17 Uniform Thickness/Gap Tolerance.5 shall not be used. 2-24. If a controlled radius is specified. See Fig. (a) For a uniform thickness feature (external). A controlled radius symbol CR creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. 2-23.15. See Fig. GM ENGINEERING STANDARDS C2B Figure 2-23 – Uniform Gap Tolerancing – Internal Feature © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 29 of 59 . C2B GM ENGINEERING STANDARDS Figure 2-24 – Uniform Thickness Tolerancing – External Feature Figure 2-25 – Uniform Thickness Tolerancing – Cylindrical Feature Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 30 of 59 October 2004 . 7). the double alpha series (AA through AZ. Letters of the alphabet (except I. O. See Fig. See Figs. or feature control frame as follows: (a) Placed on the outline of a feature surface. dimension line. 3. separated from the size dimension.6. or on an extension line of the feature outline. If there is insufficient space for the two arrows. 3-3 and 327. when the datum is the axis. or to re-identify previously established datum axes or planes on repeated or multi-sheet drawing requirements. (e) placed on the planes established by datum targets on complex or irregular datum features (see para. The symbolic means of indicating a datum feature consists of a capital letter enclosed in a square frame and a leader line extending from the frame to the concerned feature. When datum features requiring identification on a drawing are so numerous as to exhaust the single alpha series. The triangle may be filled or not filled. (b) placed on an extension of the dimension line of a feature of size when the datum is the axis or center plane. 4. The datum feature symbol is applied to the concerned feature surface outline. For CAD systems. terminating with a triangle. (d) placed on a leader line to the feature. extension line. 3 Symbology 3. (c) placed on the outline of a cylindrical feature surface or an extension line of the feature outline. BA through BZ. when the datum feature is the surface itself. Each datum feature of a part requiring identification shall be assigned a different letter. clearly October 2004 © Copyright 2004 General Motors Corporation All Rights Reserved Page 31 of 59 . See Figs. and Q) are used as datum identifying letters. 3-4(d) and (f).) shall be used and enclosed in a rectangular frame. one of them may be replaced by the datum feature triangle.3 Symbol Construction.2 Datum Feature Symbol.3. 3-2. See Figs. Where the same datum feature symbol is repeated to identify the same feature in other locations of a drawing. The triangle may be tangent to the feature. 3-4(a) through (c). 4-40.GM ENGINEERING STANDARDS C2B Figure 2-26 – Uniform Thickness Tolerancing – Formed Sheet Stock Part separated from the dimension line. or placed above or below and attached to a feature control frame controlling the feature. etc. See Fig. it need not be identified as reference. The feature control frame is related to the considered feature by one of the following methods: (a) locating the frame below or attached to a leader-directed callout or dimension pertaining to the feature. as in Fig. 3-25. See Fig. 2-23.25 Uniform Thickness/Gap Symbols. 3. 3-25. See Fig. See Figs. the notation THK follows a direct tolerance specification.3.18 All Around Symbol. The symbolic means of indicating that a tolerance applies either unilaterally or unequally disposed about the true profile. (g) placed on an extension line parallel to the center plane and separated from the size dimension. All around the part means all around the outline. 3-30 and 6-55. 3. 3-28 for RFS application and Fig. the notation GAP follows a direct tolerance specification. (c) attaching a side or an end of the frame to an extension line from the feature.3. See Fig. (e) locating the frame in a note or in a chart that clearly identifies the feature(s) to which the frame applies. For a thickness feature (external). GM ENGINEERING STANDARDS 3. 3-25.5 Feature Control Frame Placement. For a gap feature (internal). The symbolic means of indicating that a uniform Thickness/Gap tolerance applies. See Fig. 3-29 for MMC application. See Fig.24 Unequal Bilateral Symbol. See Figs.3. See Fig. 4-48 indicates that the datum feature is on the far (hidden) surface. provided it is a plane surface. 2-26. 3-25. The symbolic means of indicating that a tolerance applies to surfaces all around the part is a circle located at the junction of the leader from the feature control frame. when only one plane of a cylindrical feature of size is the desired datum. (d) attaching a side or an end of the frame to an extension of the dimension line pertaining to a feature of size. (h) the use of a dashed radial leader line. 3. (b) running a leader from the frame to the feature.C2B (f) placed above or below and attached to the feature control frame when the feature (or group of features) controlled is the datum axis or datum center plane. This symbol is used with Profile of a Line or Profile of a Surface. See Fig. 3-17. 2-24. only in the view in which the symbol is pointing to the outline. See Fig. 2-25 and Fig. 3-5 and 3-23. © Copyright 2004 General Motors Corporation All Rights Reserved Page 32 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 3-27 – Datum Feature Symbol Placement – Surface Figure 3-28 Datum Feature Placement – Feature Of Size – Rfs – One Direction © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 33 of 59 . C2B GM ENGINEERING STANDARDS Figure 3-29 – Datum Feature Placement – Feature Of Size – MMC – One Direction Figure 3-30 – Size And Proportion Of Unequal Bilateral Symbol © Copyright 2004 General Motors Corporation All Rights Reserved Page 34 of 59 October 2004 . the part may be adjusted to an optimum position. mandrel. or fabrications. respectively. Where a nominally flat surface is specified as a datum feature. (e) An unrelated actual mating envelope for a primary datum. If irregularities on the surface of a primary or secondary datum feature are such that the part is unstable (that is.2 Parts With Cylindrical Datum Features. 4. and tertiary datum features. if necessary. or centering device) is used to simulate a true geometric counterpart of the feature and to establish the datum axis or center plane. the corresponding datum is simulated by a plane contacting points of that surface. and simulated by the axis of a cylinder in the processing equipment. Surfaces D. (b) a maximum material condition boundary (MMC concept). the part is oriented and immobilized relative to the three mutually perpendicular planes of the datum reference frame in a selected order of precedence. 4. as illustrated by Fig. 4. Where a feature is referenced as a secondary (or tertiary) datum and is opposed to the datum axis (or center plane). (d) a virtual condition boundary.3 (a) Datum feature – non-opposed to a datum axis.4 Specifying Datum Features In An Order Of Precedence. A true geometric counterpart of a feature used to establish a datum may be: (a) a plane. a secondary.4. 4. See Figs. Selected datum features of in-process parts. from left to right. since they appear in that order in the feature control frame. Where a feature is referenced as a secondary (or tertiary) datum and is non-opposed (offset) to the datum axis (or center plane). machinings.2 Immobilization Of Part. 4. to simulate the datum. In fig. 4. unrelated actual mating envelope for RFS primary applications or related actual mating envelope for RFS secondary or tertiary applications). (f) a mathematically defined contour. Datum features must be specified in an order of precedence to position a part properly on the datum reference frame. it wobbles) when brought into contact with the corresponding surface of a fixture.5.3 Datum Features. vise.5 Establishing Datums. 4-2(a).3. 4-11. or secondary while the primary datum is a plane perpendicular to the cylindrical datum . secondary. 4-10. or a related actual mating envelope for a secondary or tertiary datum. 4.3 Specifying Datum Features RFS. the datum features are identified as Surfaces D. (b) Datum feature – opposed to a datum axis. 4-40(a). See Fig.5. (a) Primary Datum Feature — Diameter RFS. 4-5. E. See Fig.1 Datum Features Not Subject to Size Variations. the datum feature simulator is oriented relative to the higher ranking datums and is movable to accommodate allowable variation in the location of the datum feature. This in turn makes the geometric relationships that exist between the features measurable. such as castings. Features. A cylindrical datum feature is associated with two theoretical planes of a datum reference frame intersecting at right angles on the datum axis when the cylindrical datum is primary. the datum is established by physical contact between the feature surface(s) and surface(s) of the processing equipment. The true geometric counterpart (or unrelated actual mating envelope) is the smallest circumscribed (for an external feature) or largest inscribed (for Page 35 of 59 © Copyright 2004 General Motors Corporation All Rights Reserved . 42(b). A machine element that is variable in size (such as a chuck. Where features of a part have been identified as datum features. It is recommended that such temporary datum features not be subsequently removed by manufacturing processes. Where a datum feature of size is applied on an RFS basis. and F.3. or a tertiary datum feature. 4. The desired order of precedence is indicated by entering the appropriate datum feature reference letters. The extent of contact depends on whether the surface is a primary. (c) a least material condition boundary (LMC concept). The simulated datum is the axis of the true geometric counterpart of the datum feature. and 4-12. The datum of a cylindrical surface is the axis of the true geometOctober 2004 C2B ric counterpart of the datum feature (For example. The axis of the true geometric counterpart serves as the origin of measurement from which other features of the part are located. Figure 4-2 illustrates a part where the datum features are plane surfaces. and F are the primary. may be used temporarily to establish permanent datum features. the datum feature simulator is constrained by the basic dimensions of the drawing. These surfaces are most important to the design and function of the part.GM ENGINEERING STANDARDS 4 Datum Referencing 4. See Fig. in the feature control frame.4. See para.1 Temporary and Permanent Datum. 4-40(b). forgings. E. 4. See para. a displacement of its axis relative to the datum axis is allowed.2 Surface Primary. Where a datum feature of size is applied on an MMC basis. 4-11 and 4-12.5 of ASME Y14. (f) Datum feature of size (RFS) – opposed to a datum axis. Datum B in Fig. Where a feature of size is referenced at MMC as a secondary (or tertiary) datum and is not opposed to the datum axis or center plane. Where a feature of size is referenced at RFS as a secondary (or tertiary) datum and is not opposed to the datum axis or center plane. 442(a). 441(b).5. See para. the true geometric counterpart is constrained by the basic dimension. Furthermore.3 Cylindrical Feature at MMC Secondary. the same principle applies for widths. 415 illustrates this principle for diameters. diameter A is the secondary datum feature and RFS is applied. Variations in the size and perpendicularity of datum feature A are permitted to occur within this cylindrical boundary. where applicable. See Fig.1.2.6. See Figs. (e) Datum feature of size (RFS) – non-opposed to a datum axis. the tertiary datum (axis or center plane) is established in the same manner as indicated in (c) above with an additional requirement: The contacting cylinder or parallel planes must be oriented in relation to both the primary and the secondary datum — that is.6.5. 4. surface B is the primary datum feature. the true geometric counterpart is oriented relative to the higher ranking datums and is movable to accommodate allowable variation in the location of the feature of size. (d) Tertiary Datum Feature — Diameter or Width RFS. the related actual mating envelope relative to the primary datum. 4-18(c). 4. the size of the true geometric counterpart is determined by the specified MMC limit of size of the datum feature. machine and gaging elements in the processing equipment that remain constant in size may be used to simulate a true geometric counterpart of the feature and to establish the datum.5. Where a feature of size is referenced at MMC as a secondary (or tertiary) datum and is opposed to the datum axis or center plane. 441(a). The datum axis is the axis of the smallest circumscribed cylinder that contacts diameter A and is perpendicular to the datum plane — that is. The tertiary datum feature may be aligned with a datum axis as in Fig. In addition to size variations. (b) Primary Datum Feature — Width RFS. 4-13 and 4-14.5. the related actual mating envelope relative to the primary and secondary datum.C2B an internal feature) perfect cylinder that contacts the datum feature surface.5 Specifying Datum Features at LMC. The datum axis is the axis of a virtual condition cylinder of fixed size that is perpendicular to the datum plane B. The true geometric counterpart (or unrelated actual mating envelope) is two parallel planes at minimum separation (for an external feature) or maximum separation (for an internal feature) that contact the corresponding surfaces of the datum feature.5 shall not be used.5. 4-18(d). GM ENGINEERING STANDARDS 4. this cylinder encompasses any variation in perpendicularity between diameter A and surface B. the related actual mating envelope of a diameter that is perpendicular to datum plane B. For both external and internal features. The method in paragraph 4. or its MMC virtual condition. In Fig. the primary datum feature. (b) Datum feature of size (MMC) – opposed to a datum axis. 442(b). In each case. Where a feature of size is referenced at RFS as a secondary (or tertiary) datum and is opposed to the datum axis or center plane. For both external and internal features. In Fig. as the related actual mating envelope of datum feature A departs from its maximum size. See Fig. 4-15 or offset from a plane of the datum reference frame. See Fig. (a) Datum feature of size (MMC) – non-opposed to a datum axis. the true geometric counterpart is constrained by the basic dimensions. (c) Secondary Datum Feature RFS — Diameter or Width. the secondary datum (axis or center plane) is established in the same manner as indicated in (a) and (b) above with an additional requirement: The contacting cylinder or parallel planes of the true geometric counterpart must be oriented to the primary datum (usually a plane) — that is. the true geometric counterpart is constrained by the basic dimension. surface B is the primary datum feature. © Copyright 2004 General Motors Corporation All Rights Reserved Page 36 of 59 October 2004 . The simulated datum is the center plane of the true geometric counterpart of the datum feature. 4. 5. See Figs. See Fig. diameter A is the secondary datum feature and MMC is applied.4 Specifying Datum Features at MMC. unless otherwise specified. 4-29(b) may be used.7. When restraint is applied. 4-43 are examples of a single datum plane simulated.5 Restraining Parts Using Features Of Size. 4. 4-29(a) and 451. shall be shown on the drawing. 4-46 may be used. geometric tolerances apply with the specified datum feature(s) referenced in feature control frame(s) restrained to the nominally designed condition. Where an individual orientation or location tolerance is applied to a feature and the default restrained requirement is noted. 4. When dimensions are used to define the location of datum targets. See Figs.5.5. 4. the datum planes may be identified as shown in Fig. 4-45 may be used. The datum feature symbol shall be attached only to identifiable datum features. Where datums are established by the true geometric counterpart of datum targets.7. 4-44 may be used.6.GM ENGINEERING STANDARDS 4. a slot) of sufficient width. For controlling co-planarity of these surfaces.14 Specifying Angled Datum Features Simultaneously.7. It may be necessary to use multiple features of size to establish datum planes when the restrained requirement is invoked. When the true geometric counterpart of a datum target is movable.13 Specifying Parallel Offset Datum Features. 4-50. It is used to establish the virtual condition pins that will restrain the part in an installed condition.6.3 Specifying a Plane And a Feature of Size as a Single Datum Reference. Basic dimensions are omitted when the true geometric counterpart of datum targets are movable. 4-47 and 4-48. See Fig. The free state symbol is specified following the datum reference and any modifiers in the feature control frame. 4-50 for datum feature B (pattern of four holes) is not used to measure the free state location of the holes. Where it becomes impracticable to delineate a circular target area. Note: The position tolerance shown in Fig. such as in Fig. MAKE BOLDTo invoke the restrained requirement. Where it is desired to use parallel offset planar features to establish a datum. 4. Where it is desired to use two angled features to establish a single datum. See Fig.6. 4. Fig. 4. or by a recess (for example.7 Datums Established from Datum Targets. the method shown in Fig. See Figs. forces may be applied in accordance with the specified restraint requirement to flex or deform the part. 4. When using features of size as datum features. with controlling basic dimensions added.7. 4-51.6. 4-47 and 4-49. a note similar to the ones shown in Figs. The part surface in the area of the unrestrained datum target shall be within the tolerance specified for that surface. In order for the datum features to engage the datum feature simulators.4 Specifying The Unrestrained Requirement For A Particular Datum(s) When The Restrained Condition Is Noted. 4-20 and Fig.2 Datum Target Dimensions.2 Specifying The Restrained Requirement As Default.5. The datum target area may be indicated by section lines inside a phantom outline of the desired shape.8 Use Of Material Condition Modifiers with Restrained Datums.7.1 Simulation of a Single Datum Plane. the free state symbol may be used to indicate that the restrained requirement does not apply to particular datum features. all datum features shall contact all datum feature simulators. see Para. unless otherwise specified.3 Datum Target Areas. 4-20. This section establishes the principles and methods for defining and referencing restrained datum features. It may be desirable during dimensional measurement to restrain a part or assembly to simulate its function or interaction with other parts or assemblies. Full contact of the entire datum feature with the datum feature simulators not required. the method shown in Fig. 4.5. 4. When the feature control frame specifies a secondary or tertiFormatted: Font: Bold Formatted: Font: Bold © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 37 of 59 . a note describing the movement of the targets shall be specified. the method shown in Fig. 4. Where it is desired to use a surface and a feature of size as a single datum reference. 4.6 Datum Targets. the method of indication shown in Fig. 6. Identification of two features to establish a single datum plane may be required where separation of the features is caused by an obstruction. 4.7.7. The diameter of circular areas is given in the upper half of the datum target symbol. they shall be defined with basic dimensions. consideration must be given to the material condition (MMC or RFS) at which the datum features apply.7 Contacting Datum Simulators. In C2B these cases.5. 4.7 Restraining Datum Features. by simultaneously contacting the high points of two surfaces. 4-51.1. The part may or may not contact the unclamped datum target simulator when the datum targets define the datum plane. shields.C2B ary datum feature of size is to apply RFS. 4. When applying GD&T to some types of parts. In such cases. the location and direction is applied over the datum feature.2 Location.8. normal to the datum and the same size and shape of the datum target unless otherwise specified. 6-54. the location and direction is applied over each datum target. i.1 Application Of Force On A Restrained Datum.8 Restraining Conditions. 4. such as flexible plastics. direction and size of restraint is specified in another document. torque. The sequence of applying restraints shall be specified in the following manner: (a) On the drawing with a note. If the location. fascias.5M-1994 Para. See 4. Additional restraints may not be used unless specifically designated on the drawing. shall be noted on the product ASME Y14. 4. © Copyright 2004 General Motors Corporation All Rights Reserved Page 38 of 59 October 2004 . When this method is straining force shall be shown on specified in another document. The amount of force used to restrain a part shall be one of the following: (a) the amount required RESTRAINING the part on the datum feature simulators compliant to para 4. it is necessary to provide additional datum features in the X (length) direction. Direction and Size of Restraint on A Restrained Datum Feature. Two slots. specified in another document. (a) When datum targets are specified.7.8.8) or tertiary plane when the restrained requirement is invoked. the part may be moved on the gage within the allowable gage looseness (difference between the virtual condition boundary and the actual mating size) to optimize the part location and then clamped. etc.7.8. (b) When the entire surface is specified as the datum feature.3 Sequence Of Restraints On A Restrained Datum Reference Frame. direction and size of restraint shall be shown on the drawing or specified in another document. (b) Described in another document. the rethe drawing or If the force is the document drawing.5M Fig. See Fig. (b) The amount of force specified is equal to the force the part will be subjected to in its installed condition. 4-48 the primary datum establishes the part in the Z (height) plane. which are both called datum feature C are used for this additional support. Several considerations must be made relative to restraining a part to verify tolerances. specified.. the part is placed on the primary datum surface or datum targets.9 Pattern of Features as A Secondary or Tertiary Datum Feature. datum feature B establishes the X (length) and Y (width) planes. 4-48. In Fig. positively positioned on the RFS datum features of size and then clamped.7. In the case of secondary or tertiary datum features of size specified to apply at MMC. The location. 4. 4.5.e. normal to the datum and the same size and shape of the datum feature unless otherwise specified. it may be necessary to utilize a pattern of features to establish a secondary (ASME Y14. the document shall be noted on the product drawing. the range of accept- GM ENGINEERING STANDARDS able force (clamp load. or covers. Because the part is not rigid.) shall be used. with reference to the other document on the drawing. GM ENGINEERING STANDARDS C2B Figure 4-40 – Interpretation For Secondary (Or Tertiary) Datum Feature Where Next Higher Ranking Datum Is An Axis (Or Center Plane) – Secondary (Or Tertiary) Datum Feature Is A Plane © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 39 of 59 . C2B GM ENGINEERING STANDARDS Figure 4-41 – Interpretation For Secondary (Or Tertiary) Datum Feature Where Next Higher Ranking Datum Is An Axis (Or Center Plane) – Secondary (Or Tertiary) Datum Feature Is A Feature Of Size – RFS © Copyright 2004 General Motors Corporation All Rights Reserved Page 40 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 4-42 – Interpretation For Secondary (Or Tertiary) Datum Feature Where Next Higher Ranking Datum Is An Axis (Or Center Plane) – Secondary (Or Tertiary) Datum Feature Is A Feature Of Size – MMC © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 41 of 59 . C2B GM ENGINEERING STANDARDS Figure 4-43 – Method Of Specifying Coplanar Datum Features – Common Plane Figure 4-44 – Method Of Specifying Coplanar Datum Features – Parallel Offset Planes © Copyright 2004 General Motors Corporation All Rights Reserved Page 42 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 4-45 – Using Angled Part Features As Datum Features © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 43 of 59 . C2B GM ENGINEERING STANDARDS Figure 4-46 – Surface And Feature Of Size At MMC. Single Datum Reference © Copyright 2004 General Motors Corporation All Rights Reserved Page 44 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 4-47 – Indication Of Unrestrained Datum Targets © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 45 of 59 . C2B GM ENGINEERING STANDARDS Figure 4-48 – Multiple Features Of Size As A Secondary Or Tertiary Datum Feature © Copyright 2004 General Motors Corporation All Rights Reserved Page 46 of 59 October 2004 . GM ENGINEERING STANDARDS C2B Figure 4-49 – Specifying Restrained Datum © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 47 of 59 . C2B GM ENGINEERING STANDARDS Figure 4-50 – Part Restrained On Features Of Size © Copyright 2004 General Motors Corporation All Rights Reserved Page 48 of 59 October 2004 . 3. A positional tolerance applied at MMC ceeded and still satisfy function and intermay be explained in either of the following ways. Where the unrelated actual mating size is larger than MMC. the speci5. terms of the surface. its axis must fall 5.2. The diameter of this features (such as a group of mounting holes) zone is equal to the positional tolerance. Where datum face. Where datum feature B is at defines the limits of variation in the orientation of MMC. not be exactly equivalent to the tolerance in See Fig. its axis may be at MMC that the specified tolerance zone apdisplaced relative to the location of the datum plies. 5-8. 5-5. is at MMC (minimum diameter). (a) In Terms of the Surface of a Hole. In many instances.3 Fundamental Explanation of Positional tion limit of size (MMC) and the unrelated actual Tolerancing. the tolerance in terms of the axis may theoretical boundary located at true position. 5-6(a) and (b).3. While Note: In certain cases of extreme form deviation maintaining the specified size limits of the hole. It is only where the hole is feature B departs from MMC. additional positional © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 49 of 59 . the surface (b) In Terms of the Axis of a Hole. See must be positioned relative to a datum feature at Figs. mating size of the hole. a group of located at true position. See Fig. (within limits of size) or orientation deviation of no element of the hole surface shall be inside a the hole. changeability requirements. 5-6(c). This tolerance zone also MMC.2. 5-7.1 Explanation of Positional Tolerance at fied positional tolerance for a hole may be exMMC. See Fig. its axis determines the location of the the axis of the hole in relation to the datum surpattern of features as a group. See Fig. Where a hole interpretation shall take precedence.2 Displacement Allowed by Datum Feawithin a cylindrical tolerance zone whose axis is tures at MMC. Where the unrelated actual mating size of axis (datum B at MMC) in an amount equal to the hole is larger than MMC.GM ENGINEERING STANDARDS C2B Figure 4-51 – Datum Target Areas tolerance results. In such cases. This increase of positional tolerance is equal to the difference 5 Tolerances of Location between the specified maximum material condi5. 11. the positional tolerance allowed is in direct proportion to the actual clearance hole size as shown by the following tabulation: Clearance Hole Diameter (Feature Unrelated Actual Mating Size) 14 14.5 Positional Tolerance Diameter Allowed 0 0.1 0. 5-10 is zero at MMC.3 0.8 Symmetrical Relationships Using Positional Tolerance Without a Datum Reference. the feature surfaces must be within the coaxial virtual conditions simultaneously. 5.25 14.3.1 Example of Zero Positional Tolerance at MMC. If the position tolerance is applied MMC. a positional tolerance of some magnitude is specified for the location of features.3 14.C2B one-half the difference between its actual mating size and MMC size.3. but produced to a size smaller than the specified minimum (outside of limits). had been displaced relative to the axis of the datum feature’s actual mating envelope. In certain cases. However. Where a part has two or more coaxial diameters. and specifying a zero positional tolerance at MMC.1 14. provided features are within size limits. 5. This requirement imposes a closer control of the features involved and introduces complexities in verification. requires the axis of each feature to be located within the specified positional tolerance regardless of the size of the feature. where applied to the positional tolerance of circular features. If the position tolerance is applied RFS. the design or function of a part may require the positional tolerance. However. but the minimum was adjusted to correspond with a 14 mm diameter fastener. the positional tolerance allowed is totally dependent on the unrelated actual mating size of the considered feature. Note: The actual mating envelope would be unrelated for a primary datum feature and related for a secondary or tertiary datum feature.11. 5. the shift of the axis of the datum feature is automatically accommodated. This is accomplished by adjusting the minimum size limit of a hole to the absolute minimum required for insertion of an applicable fastener located precisely at true position. 5. to be maintained regardless of the features’ unrelated actual mating sizes. the increase being equal to the conventional positional tolerance specified in Fig.4 RFS as Related to Positional Tolerancing.3. RFS. or both. this must be taken into account. no datum references are specified. and only the interrelationship between the features of size is controlled with position tolerance. The application of MMC permits the tolerance to exceed the value specified. In this case.4 14. rejection of usable parts can occur where these features are actually located on or close to their true positions. if open set-up inspection methods are used to check the location of the feature pattern relative to the axis of the datum feature’s actual mating envelope. as a group. as explained in para.2 14.3. The principle of positional tolerancing at MMC can be extended in applications where it is necessary to provide greater tolerance within functional limits than would otherwise be allowed.1. 2.11 Coaxiality Controls. 59.4 0. Note that the maximum size limit of the clearance holes remains the same. This results in an increase in the size tolerance for the clearPage 50 of 59 GM ENGINEERING STANDARDS ance holes. the October 2004 © Copyright 2004 General Motors Corporation All Rights Reserved .8.2 0. 5-63 and 5-64. This relative shift of the pattern of features.5 5.7 Coaxial Relationships Using Positional Tolerance Without a Datum Reference. Although the positional tolerance specified in Fig.1.3.3 Zero Positional Tolerance at MMC. Where a part has two or more coaxial diameters. Figure 5-10 shows a drawing of the same part with a zero positional tolerance at MMC specified. See Figs. datum reference. 5.25 0. the features are therefore viewed as if they. and the feature locations are such as to make the part acceptable. In the preceding explanation. Note: If a functional gage is used to check the part. no datum references are specified. If the position tolerance is applied RFS. and only the interrelationship between the features of size is controlled with position tolerance. with respect to the axis of the datum feature does not effect the positional tolerance of the features relative to one another within the pattern. Since the axis of the datum features actual mating envelope must serve as the origin of measurements for the pattern of features. the axes of the unrelated actual mating envelopes must be within the specified cylindrical tolerance zone simultaneously. as a group. Paragraph 5. Positional tolerancing for symmetrical relationships is that condition where the center plane of the unrelated actual mating envelope of one or more features is congruent with axis or center plane of a datum feature within specified limits. When datums are specified.2 of ASME Y14. The collective effects of the MMC condition of the stated size tolerance and the associated position tolerance define the boundary. 5-65. 5. See Fig.14 Symmetry Tolerancing to Control the Median Points of Opposed or Correspondingly Located Elements of Features. Paragraph 5. If the position tolerance is applied MMC.12.13 Positional Tolerancing For Symmetrical Relationships. An MMC modifier must be specified in the tolerance portion of the feature control frame. C2B 5. 5.5 shall not be used.12.12 Concentricity.12. Paragraph 5.14 of ASME Y14.5 shall not be used. the feature surfaces must be within the coaxial virtual conditions simultaneously. 5.5 shall not be use. 5.2 Difference Between Coaxiality Controls and Concentricity. The tolerance applies to the extent defined by the between specification including the bend areas. When datums are not specified. such as a tube. the tolerance specification controls the form and the interrelationship between the applicable features. To constrain the boundary of a nominally cylindrical part with bends.16 Position Of A Cylindrical Part With Bends.12. the position symbol is used in the feature control frame with the between symbol specified beneath. or RFS modifiers may be specified to apply to both the tolerance and the datum feature. hose or rod.1 Concentricity Tolerancing.1 of ASME Y14.GM ENGINEERING STANDARDS axes of the unrelated actual mating envelopes must be within the specified cylindrical tolerance zone simultaneously. 5. IMC. © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 51 of 59 . the form is constrained by the boundary established by the position or orientation control. MMC. C2B GM ENGINEERING STANDARDS Figure 5-63 – Coaxial Features Of Size – Same Size – Without Datum Reference Figure 5-64 – Coaxial Features Of Size – Different Sizes – Without Datum Reference © Copyright 2004 General Motors Corporation All Rights Reserved Page 52 of 59 October 2004 . When specifying a profile of a surface tolerance unilaterally or unequal disposed bilaterally. 6-18. 6-16. and location. It is used to control form or combinations of size. form. (a) An appropriate view or section is drawn showing the desired basic profile. Orientation.GM ENGINEERING STANDARDS C2B Figure 5-65 – Position Tolerancing Of A Nominally Cylindrical Feature Of Size With Bends (b) Unilaterally and unequally disposed profiles may be specified in a feature control frame with a leader directed to the surface.) 6 Tolerances of Form. and Runout 6.5 the method of specifying unilateral or unequal bilateral profile tolerancing is replaced by the method described in this addendum: Figs: 6-11. © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 53 of 59 . 6. See Figs. the Unequal Bilateral symbol is added to the feature control frame following the tolerance value. Where used as a refinement of size.5. Profile. 6-15. orientation.5 Profile Control. The profile tolerance specifies a uniform boundary along the true profile within which the elements of the surface must lie. Profile tolerances are specified as follows.1 Profile Tolerancing. (In the following figures of Y14. A second value is added following the Unequal Bilateral symbol to indicate the amount of the tolerance that applies outside of the material. 3-30 and 6-55. the profile tolerance must be contained within the size limits. See Fig. and the entire feature surface must lie outside the boundary. Datum referencing in the upper segment of a composite profile feature control frame serves to locate the feature profile locating tolerance zone relative to specified datums.e. center plane. 3-18 and 6-54. which the surface or center plane of the considered feature must lie. 6. See Fig. The tolerance values represent the distance between two boundaries disposed about the true profile as defined by the basic dimensions and respective applicable datums. 6-14. See Fig.8 Free State Variation. Each feature is located from specified datums by basic dimensions. Angularity is the condition of a surface. the extent of the profile tolerance must be indicated. 6-53.6. See Figs.8. (b) a tolerance zone defined by two parallel planes at the specified basic angle from one or more datum planes or a datum axis.8. the term BOUNDARY is placed beneath the positional tolerance feature control frame.2 Angularity. (c) A cylindrical tolerance zone at the specified basic angle from one or two datum planes. 6. See Figs. GM ENGINEERING STANDARDS 6. The lower segment serves to establish the limits of form and/or size.6. 6-28.5. 6-56. within. When datums are specified in the lower segment. 6-25 and 6-26. or a datum axis within which the axis of the considered feature of size must lie. the boundary equals the MMC size of the profile minus the positional tolerance. 6-29 (d) a tolerance zone defined by two parallel lines at the specified basic angle from a datum plane or axis. See Figs. the basic dimensions and the profile tolerance establish a tolerance zone to control the shape and size of the feature.. 6-27. 6. to clarify a free state requirement on a drawing containing restrained feature notes. Additionally. See Fig. Similarly. See Fig. For an internal feature. the boundary equals the MMC size of the profile plus the positional tolerance. 6-12. and the entire feature surface must lie within the boundary.2 Specifying Geometric Tolerances on Features to Be Restrained When a general restraint note is specified on the drawing. specify the maximum allowable free state variation with an appropriate feature control frame. The free state symbol may be placed within the feature control frame. within.2. the extent of each profile tolerance may be indicated by the use of reference letters to identify the extremities or limits of each requirement.1 Specifying Geometric Tolerances on Features Subject to Free State Variation. See Fig. Where segments of a profile have different tolerances.C2B (c) Where a profile tolerance applies all around the profile of a part. 6. To invoke this concept. all geometric tolerances shall be within stated values unless otherwise specified. © Copyright 2004 General Motors Corporation All Rights Reserved Page 54 of 59 October 2004 .6 Orientation Tolerances. For an external feature. following the tolerance and any modifiers.5.9. 6. In this example. or axis at a specified angle from a datum plane or axis. Where tolerance is applied to a feature in the free state. which the line element of the surface must lie. The actual surface of the controlled feature must lie within both the profile locating tolerance zone and the profile size/form/orientation tolerance zone. the positional tolerance establishes a theoretical boundary shaped identically to the basic profile. 6-25 and 6-26. An angularity tolerance specifies one of the following: (a) a tolerance zone defined by two parallel planes at the specified basic angle from one or more datum planes or a datum axis. which the axis of the considered feature must lie.1.1 Angularity Tolerance. Geometric tolerances applied as a boundary control for a noncylindrical feature (i. 6.5. Profile tolerancing may be combined with positional tolerancing where it is necessary to control the boundary of a noncylindrical feature. 6. See Fig.1 Explanation of Composite Control. within. or to separate a free state requirement from associated features having restrained requirements. if some segments of the profile are controlled by a profile tolerance and other segments by individually toleranced dimensions. the symbol used to designate “all around” is placed on the leader from the feature control frame.1 Boundary Control for a Noncylindrical Feature. 6-13. position or orientation controls) may be specified with a single leader line as shown in Fig. See Fig 6-56. the tolerance zone is oriented to the datums. GM ENGINEERING STANDARDS C2B Figure 6-55 – Specifying Unequal Profile Tolerance © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 55 of 59 . C2B GM ENGINEERING STANDARDS Figure 6-56 – Boundary Principle With Unequal Profile Tolerance © Copyright 2004 General Motors Corporation All Rights Reserved Page 56 of 59 October 2004 . When calculating positional tolerancing. C2B © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 57 of 59 .GM ENGINEERING STANDARDS Appendix B – Formulas For Positional Tolerancing B1 General The purpose of this Appendix is to present formulas for determining the required positional tolerances or the required sizes of mating features to ensure that parts will assemble. Consideration must be given for additional geometric conditions that could affect functions not accounted for in the following formulas. no clearance” fit when features are at maximum material condition with their locations in the extreme of positional tolerance. need to be considered to ensure assembly. The formulas are valid for all types of features or patterns of features and will give a “no interference. conditions such as fastener straightness. and projected fastener length. thread to shank run out. an increase in the parallelism tolerance is allowed which is equal to such departure.2 diameter cylindrical zone inclined 60° to datum plane A. 5-60 change "The center plane of datum feature B is perpendicular to datum plane A" to "Center plane of the related actual mating envelope of datum feature B perpendicular to datum plane A". Where the unrelated actual mating envelope of the feature departs from its MMC size. 6-32 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". 4-18(b) change (Smallest circumscribed cylinder) to (Unrelated actual mating envelope). the feature axis must lie within a 0. the axis of the unrelated actual mating envelope of the feature must lie between two parallel planes 0. 6-28 change "Regardless of feature size." Fig.05 diameter. 4-15 change (Parallel planes at maximum separation perpendicular to datum plane A. Fig. The feature axis must be within the specified tolerance of location" to "Regardless of feature size. Fig. The feature axis must be within the specified tolerance of location" to "Regardless of feature size.2 diameter cylindrical zone inclined 60° to datum plane A”. Center plane aligned with datum axis B. 6-31 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". the axis of the unrelated actual mating envelope of the feature must lie within a 0. GM ENGINEERING STANDARDS Fig. 4-12 change (Largest inscribed cylinder) to (Unrelated actual mating envelope). Fig. F1 General Fig. the axis of the unrelated actual mating envelope of the feature must lie within a 0. Fig.5. Fig. Change the note in the MEANS THIS to read "When the unrelated actual mating envelope is at its maximum material condition (10. 4-21 change smallest pair of coaxial circumscribed cylinders to Related actual mating envelope (Smallest pair of coaxial circumscribed cylinders). Fig. 4-18(c) change (Smallest circumscribed cylinder perpendicular to datum plane B) to (Related actual mating envelope perpendicular to datum plane B). Change the note in the MEANS THIS to read "Regardless of feature size. the axis of the unrelated actual mating envelope of the feature of size must lie between two parallel planes 0.12 apart. 4-14 change (Parallel planes at maximum separation) to (Unrelated actual mating envelope). Fig. The axis of the unrelated actual mating envelope must be within the specified tolerance of location. 6-29 change "Regardless of feature size. Fig.00). the maximum parallelism tolerance is 0. 5-56 change "Axis of actual mating envelope" to "Axis of related actual mating envelope". The axis of the unrelated actual mating envelope of the feature must be within the specified tolerance of location.C2B Appendix New F – Effect Of Changes To The Definition Of Actual Mating Envelope On The Figures In Y14. Fig. the feature axis must lie between two parallel planes 0. 5-57 change "Axis of actual mating envelope" to "Axis of related actual mating envelope". Center plane aligned with datum axis B.2 diameter cylindrical zone parallel to datum axis A. 6-33 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". Fig. Change the note in the MEANS THIS to read "Regardless of feature size. Fig.2 apart which are inclined 60° to datum plane A”. 4-13 change (Parallel planes at minimum separation) to (Unrelated actual mating envelope). The axis of the unrelated actual mating envelope must be within the specified tolerance of location.) To (Related actual mating envelope perpendicular to datum plane A.2 apart which are inclined 60° to datum plane A. 5-61 change "The center plane of datum feature A" to "Center plane of the unrelated actual mating envelope of datum feature A".) Fig. Fig. October 2004 © Copyright 2004 General Motors Corporation All Rights Reserved Page 58 of 59 . 4-11 change (smallest circumscribed cylinder) to (unrelated actual mating envelope)." Fig. 4 diameter.GM ENGINEERING STANDARDS Fig.00). In the note in the MEANS THIS change second and third sentences to read "Where the feature's unrelated actual mating envelope departs from its MMC size." Fig. The center plane of the unrelated actual mating envelope of the feature must be within the specified tolerance of location. Change the note in the MEANS THIS to read "Where the unrelated actual mating envelope of the feature is at its maximum material condition (50. Fig. a perpendicularity tolerance is allowed which is equal to such departure. an increase in the perpendicularity tolerance is allowed equal to the amount of such departure." Fig. a perpendicularity tolerance is allowed which is equal to such departure. The axis of the unrelated actual mating envelope of the feature must be within the specified tolerance of location. Change the note in the MEANS THIS to read "Regardless of feature size. 6-39 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope".2 apart which are perpendicular to axis of the unrelated actual mating envelope of datum feature A. its axis must be perpendicular to datum plane A.00). C2B Fig.12 apart. the center plane of the unrelated actual Mating envelope of the feature must lie between two parallel planes 0. Change the note in the MEANS THIS to read "Where the unrelated actual mating envelope of the feature is at its maximum material condition (50." © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 59 of 59 . Change the note in the MEANS THIS to read "Regardless of feature size. The axis of the unrelated actual mating envelope must be within the specified tolerance of location. The axis of the unrelated actual mating envelope of the feature must be within the specified tolerance of location. Where the unrelated actual mating envelope of the feature departs from MMC. Change the note in the MEANS THIS to read "Regardless of feature size. 6-42 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". which are perpendicular to datum plane A. the axis of the unrelated actual mating envelope of the feature must lie between two parallel planes 0. Where the unrelated actual mating envelope of the feature departs from MMC." Fig.1 maximum. 6-41 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". the axis of the unrelated actual mating envelope of the feature must lie within a cylindrical tolerance zone 0. 6-38 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". 6-40 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". which is perpendicular to and projects from datum plane for the feature height. 6-36 change "Possible orientation of feature center plane" to Possible orientation of center plane of unrelated actual mating envelope". up to 0. its axis must be perpendicular to datum plane A." Fig. The axis of the unrelated actual mating envelope of the feature must be within the specified tolerance of location. 6-37 change "Possible orientation of feature axis" to Possible orientation of axis of unrelated actual mating envelope". The axis of the unrelated actual mating envelope of the feature must be within the specified tolerance of location.