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ENGINEERINGSTANDARDS Design StandardElectronicC2B Global Dimensioning And Tolerancing Addendum – 2004 © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Originating Department: North American Engineering Standards Page 1 of 59 Contents Foreword…………………………………..2GM Acknowledgement…………………....2Automotive Industry RepresentativeAcknowledgment……………...…………..2Structure………………………………..….2General Motors Authorization…………….2Figures…………………………………….3Titleblock Notes…………..…………….…3 Section 1Scope, Definitions, and GeneralDimensioning 1.3 Definitions……………………………..41.4 Fundamental Rules…………………….71.5 Units of Measurement…………………81.6 Application of Dimensions……………81.7 Dimensioning Features………………..81.8 Location of Features……………….….9 Section 2General Tolerancing and Related Principles 2.7 Limits of Size…………………..…….252.8 Applicability of RFS, MMC, andLMC………………………………..…….262.15 Radius………………………………272.16 Statistical Tolerancing……..……….272.17 Uniform Thickness/Gap Toler-ance…………………………………27 Section 3Symbology 3.3 Symbol Construction………………...323.5 Feature Control Frame Placement…...32 Section 4Datum Referencing 4.2 Immobilization of Part………..……...354.4 Specifying Datum Features in anOrder of Precedence………...…….……...354.5 Establishing Datums…………………354.6 Datum Targets………………………..374.7 Restraining Datum Features………….374.8 Restraining Conditions…………….…38 Section 5Tolerances of Location 5.3 Fundamental Explanation of Positional Tol-erancing………………………………505.11 Coaxiality Controls…………………515.12 Concentricity………………………..515.14 Symmetry Tolerancing……………...515.16 Cylindrical Part with Bends………...51 Section 6Tolerances of Form, Profile, Orientation, andRunout 6.5 Profile Control……………………….536.6 Orientation Tolerances……………….546.8 Free State Variation………………….54 APPENDIX BFormulas for Positional Tolerancing B1 General……………………………….57 Appendix New FEffect of Changes to the Definition of ActualMating Envelope on the Figures in Y14.5 F1 General………………………………..57 C2B GM ENGINEERING STANDARDS © Copyright 2004 General Motors Corporation All Rights Reserved Page 2 of 59 October 2004 Foreword General Motors Corporation and Delphi Corpora-tion have adopted an amended version of theASME Y14.5M-1994 dimensioning and toleranc-ing standard (amended by this addendum) foruse by the above companies on all product engi-neering documentation.This addendum was created to address the fol-lowing areas:1. Select an option from ASME Y14.52. Clarify a concept from ASME Y14.5 3. Discourage/disallow the use of a conceptfrom ASME Y14.5 4. Include a concept not covered by ASMEY14.5All other standards referenced in ASME Y14.5have not necessarily been adopted by the abovecompanies, and are not automatically invoked.Current company standards will take precedenceunless otherwise noted. GM Acknowledgment This document represents the consensus of themembers of the GM GD&T Task Team.GM GD&T contributing members:Michael A. Murphy, GMPTRobert Bourland, GMPTGuy Browne, HoldenThomas Drexler, OpelAnders Gustavsson, SaabJames Gyomber, HoldenGisela Herzing, GM RuesselsheimAlex Krulikowski, GMPTDale MacPherson, GMPTCliff McCord, NAVOTibor Nuebl, OpelHans-Olof Svensson, SaabSusan Belloli, GMPTKlaus W. Schulz, Opel Powertrain GmbHAndy Watts, NAVODuane Harbowy, GMPT Automotive Industry Representative Ac-knowledgment This addendum also represents input of thefollowing automotive industry representatives:Neil Freson, Delphi Energy & Chassis SystemsPaul Sams, Delphi Delco Electronics SystemsDave Arnold, Delphi Safety & Interior SystemsJames Anderson, Delphi Harrison Thermal Sys-temsBruce Eggert, Delphi Harrison Thermal SystemsDan Meyers, Delphi Delco Electronics SystemsJamie Florence, Aerotec (figure construction) General Motors Authorization This standard is authorized by the GM GlobalEngineering Design Committee Notice of Action# GEDC 162. Structure The paragraph numbering in this addendum isas follows: Paragraphs are generally numberedto coincide with numbers in ASME Y14.5. Para-graph numbers preceded by “NEW” are addi-tions to Y14.5. Unless otherwise noted, para-graphs not preceded by “NEW” replace theparagraph in Y14.5 that is identified by the samenumber. Italicized text may be added, followingthe paragraph title noting whether the paragraphis a deletion or to describe the changes to anexisting paragraph in Y14.5. Paragraph refer-ences noted in the figures refer to the para-graphs contained in this document. Figures ref-erenced in the text but not shown in this adden-dum are found in Y14.5.Paragraph titles contained in parenthesis are forindex referencing only and do not reflectchanges to Y14.5.The words “shall/must/required” describe strictrequirements. Procedural steps defined bythese words must be followed.The words “should/preferred/recommended”describe preferences. Procedural steps definedby these words must be followed whenever thereis no valid reason to do otherwise.The words “acceptable/allowed/may/might” grantpermission. They do not require or recommendthe practice they specify; neither do they forbidor discourage alternative practices. GM ENGINEERING STANDARDS C2B © Copyright 2004 General Motors Corporation All Rights Reserved October 2004 Page 3 of 59 Figures The figures in this Addendum exhibit the arrowmethod of view projection. GM EngineeringStandards – Drawing Views and Sections (C3) Titleblock Notes The note shown in Fig. F-1 shall appear ondrawings, documents or within databases whichare in accordance with the General MotorsGlobal Dimensioning and Tolerancing Adden-dum – 2004. The note shall be in the title block(or in the general notes). The note invokes thisaddendum.THIS DOCUMENT IS IN ACCORDANCE WITHASME Y14.5M-1994 AS AMENDED BY THEGM GLOBAL DIMENSIONING ANDTOLERANCING ADDENDUM – 2004. Figure F-1 – Note To Invoke Gm GlobalDimensioning And Tolerancing Addendum –2004 C2B GM ENGINEERING STANDARDS © Copyright 2004 General Motors Corporation All Rights Reserved Page 4 of 59 October 2004 1 Scope, Definitions, and GeneralDimensioning 1.3 Definitions.1.3.3 Datum. A theoretically exact point, axis,line, or plane derived from the true geometriccounterpart. A datum is the srcin from whichthe location or geometric characteristics of fea-tures of a part are established. 1.3.5 Datum Feature Simulator. A surface of adequately precise form (such as a surfaceplate, a gage surface, fixture pad, pin, centeringdevice, or a mandrel) used to establish the simu-lated datum(s).Note: Datum feature simulators are used as thepractical embodiment of the datums duringmanufacture and inspection. 1.3.7 Datum Target. A specified point, line, orarea on a drawing that represents a theoreticallyperfect fixture element. 1.3.9 Dimension, Basic. A numerical valueused to describe the theoretically exact size,profile, orientation, or location of a feature; orien-tation or location of feature of size; or datumtarget. See Fig. 3-7. It is the basis from whichpermissible variations are established by toler-ances on other dimensions, in notes, or in fea-ture control frames. See Figs. 2-14, 2-15, and 3-25. Title block or general plus/minus tolerancesdo not apply to basic dimensions. 1.3.11 Envelope, Actual Mating. A generalterm used to refer to an unrelated or relatedactual mating envelope. Note: Changes to the definition of Actual MatingEnvelope have had numerous effects on figuresin Y14.5. Appendix NEW F outlines the effectson figures in Y14.5. 1.3.11.1 Envelope, Unrelated Actual Mating. An unrelated actual mating envelope, (unrelatedto a datum reference frame), can be eitherexternal or internal as described below:(a) For an external feature of size, a similar per-fect feature counterpart of smallest size that canbe circumscribed about the feature of size sothat it contacts the surface or surfaces. Forexample, a smallest cylinder of perfect form ortwo parallel planes of perfect form at minimumseparation that contacts the surface(s). See Fig.1-57.(b) For an internal feature of size, a similar per-fect feature counterpart of largest size that canbe inscribed within the feature of size so that itcontacts the surface or surfaces. For example,a largest cylinder of perfect form or two parallelplanes of perfect form at maximum separationthat contacts the surface(s). 1.3.11.2 Envelope, Related Actual Mating. Arelated actual mating envelope, (related to adatum reference frame), can be either externalor internal as described below:(a) For an external feature of size datum feature,a similar perfect feature counterpart of smallestsize that can be circumscribed about the featureof size so that it contacts the surface or sur-faces. For example, the smallest cylinder ofperfect form or two parallel planes of perfectform at minimum separation that contacts thesurface(s). This envelope is oriented relative tothe appropriate datum(s), See Fig. 1-57.(b) For an internal feature of size datum feature,a similar perfect feature counterpart of largestsize that can be inscribed within the feature ofsize so that it contacts the surface or surfaces.For example, the largest cylinder of perfect formor two parallel planes of perfect form at maxi-mum separation that contacts the surface(s).This envelope is oriented relative to the appro-priate datum(s). 1.3.12.1 Feature, Interrupted. A feature, (sur-face), that has an interruption. The keywordINTERRUPTED is placed adjacent to a sizedimension, feature control frame or the datumfeature symbol indicating that the specified toler-ance zone, size dimension or datum featureapplies through the interruption. See fig. 1-59. 1.3.13 Feature of Size, Axis Of. A straight linethat coincides with the axis of the unrelated ac-tual mating envelope of a feature of size. SeeFig. 1-57. 1.3.14 Feature of Size, Center Plane Of. Aplane that coincides with the center plane of theunrelated actual mating envelope of a feature ofsize. 1.3.15 Feature of Size, Derived Median PlaneOf. An imperfect plane (abstract) that passesthrough the center points of all line segmentsbounded by the feature of size. These line seg-ments are normal to the unrelated actual matingenvelope. 1.3.16 Feature of Size, Derived Median LineOf. An imperfect line (abstract) that passesthrough the center points of all cross sections ofthe feature of size. These cross sections are
