1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER: (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1999 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001STANDARDSubmitted for recognition as an American National StandardJ390RE
4、V.MAY1999Issued 1970-07Revised 1999-05Superseding J390 JUN1982(R) Dual Dimensioning Engineering DrawingsForewordThis Document also changed to comply with the new SAE Technical Standards Board format. Scope isSection 1, References, Section 2. All other section numbers have changed accordingly.1. Scop
5、eThis document covers a dual dimensioning practice that provides both U.S. customary inch-poundunits and SI metric units for all dimensions on the field of the drawing. The scope does not include the variousmethods by which computer programs are used for dual dimensioning. In one method that has had
6、 someusage, drawings are dimensioned in SI (metric) units, with conversions to U.S. customary inch-pound unitsprovided in a computer-generated chart on the drawing.1.1 PurposeThe purpose of this document is to provide an authoritative guide for uniform application of dualdimensioning on engineering
7、drawings. SAE recognizes that a decision regarding measurement units is anindividual judgment based on needs and circumstances. While providing this information, SAE takes noofficial position concerning dual dimensioning. Issuance of this publication should not be construed asadvocacy.1.2 GeneralInt
8、roductionThis document establishes a uniform method of combining inch-pound units andmetric units of measure on the same engineering drawing. In this document “metric units” means theInternational System of Units (abbreviated SI) as described in SAE TSB 003. Herein is guidance forconverting from one
9、 system to the other while maintaining functional interchangeability.2. References2.1 Applicable PublicationsThe following publications form a part of the specification to the extent specifiedherein. Unless otherwise indicated, the latest revision of SAE publications shall apply.2.1.1 SAE PUBLICATIO
10、NSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE TSB 003Rules for SAE Use of SI (Metric) Units2.1.2 ANSI PUBLICATIONAvailable from ANSI, 11 West 42nd Street, New York, NY 10036-8002.ANSI Y14.5IEEE/ASTM SI 10Standard for Use of the International System of Units (SI): The Mo
11、dern Metric SystemNOTEThis American National Standard is available from ANSI and also from:IEEE, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331.ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling Servi
12、cesSAE J390 Revised MAY1999-2-3. Standard Units3.1 Inch-Pound UnitsThe inch-pound unit for linear dimensions is the inch with decimal dimensioning preferred.(One inch equals 25.4 mm, exactly.)3.2 Metric UnitsThe metric unit, on engineering drawings, for linear dimensions is the millimeter.3.3 Identi
13、fication of UnitsThe inch and millimeter dimensions must be identified, one from the other as follows:3.3.1 ALTERNATIVE METHODSIt is permissible to use one of the following methods of identification:a. Dimensions may be identified by relative position with the millimeter dimension above or to the le
14、ft ofthe inch dimensions.FIGURE 1ALTERNATIVE METHODS FOR DUAL DIMENSIONINGb. Position method as in (a) except with inch dimension above or to the left of the millimeter dimension.c. Square brackets surrounding the millimeter dimensions, placed adjacent to the inch dimensions(position optional).d. Sq
15、uare brackets surrounding the inch dimensions, placed adjacent to the millimeter dimensions(position optional).3.3.2 Only one of the previous methods of identification of units shall be used throughout a single drawing. Eachdrawing shall illustrate how to identify the inch and millimeter dimensions,
16、 by a note adjacent to or within thetitle block, such as:FIGURE 2ENGINEERING DRAWING TITLE BLOCK NOTEFOR DUAL DIMENSIONINGor by reference to a drawing interpretation specification.3.3.3 In converting existing drawings to dual-dimensioning, space limitations may sometimes make it impractical tolocate
17、 dimensions as required for identification by position. In these cases, it is permissible to show theconverted dimension in a nearby associated location identified with the symbol mm or IN.3.3.4 Units other than linear and all units used for other than normal drawing dimensions (e.g., notes or text)
18、 shallbe identified with the appropriate symbol.EXAMPLE13.6 Nm/10 lbfftOVERHANG LIMITED TO 12.7 mm/.50 inCOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J390 Revised MAY1999-3-3.4 Common UnitsSome units can be stated so that the call-out will satisfy the u
19、nits of both systems. That is,.06 inch per inch or 0.06 millimeter per millimeter can both be expressed simply as a ratio, 0.06:1, or in a note,such as TAPER 0.06:1.3.5 AnglesAngular dimensions need no conversion. Angles stated in degrees and decimals of a degree, or indegrees, minutes, and seconds
20、are common to the inch-pound and metric systems of measurement.3.6 Nominal DesignationsNominal designations such as thread sizes and tire sizes will not be converted.4. Principles4.1 Millimeter Dimensioning Practices4.1.1 A zero precedes a decimal point in a millimeter value of less than one;EXAMPLE
21、0.134.1.2 Where unilateral tolerancing is used and either the plus or minus value is nil, this value shall be expressed bya single zero only.EXAMPLE4.1.3 Nonsignificant zeros are not shown after the decimal point, in the composition of a millimeter value, exceptas follows:a. Where limit dimensioning
22、 is used and either the maximum or minimum dimension has digits followingthe decimal point, the other value shall have zeros added for uniformity.EXAMPLEb. Where bilateral tolerancing is used, both the plus and minus values shall have the same number ofdecimal places, using zeros where necessary.EXA
23、MPLE4.1.4 The symbol and the abbreviation DIA are synonymous, defining a feature as diametral. Either may beused on a dual dimension drawing; however, both shall not be used on the same drawing. The application ofeither the symbol or DIA is self explanatory. The symbol may either precede or follow t
24、he dimension:EXAMPLE4.1.5 The decimal sign for metric values shall be the same as that used for the inch decimal dimension, a dot (.).4.1.6 Commas and spaces shall not be used to denote thousands in either inch or metric values.EXAMPLE32541 not 32,541 nor 32 54132 00.02 32+0.02025.0025.45not 2525.45
25、32+0.250.10 not 32+0.250.1 25.41.00- or 25.41.00-COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J390 Revised MAY1999-4-5. Application5.1 New DrawingsDual dimensioning of new drawings is facilitated if all dimensions are shown in decimals.5.2 General Toler
26、ancesGeneral tolerances usually expressed on a drawing as part of the format or as ageneral note shall be dual dimensioned.5.3 SymbolsGeometric characteristic symbols for form and position and the related tolerancing procedure arerecommended to be used on dual dimensioned drawings. See ANSI Y14.5.5.
27、3.1 Dual dimensioned drawings shall specify, by the ISO symbol as shown in Figure 3, the angle of projectionused. Although first angle projection is commonly used in many countries where the metric measurementsystem is standard, it is recommended that third angle projection be used on dual dimension
28、ed drawings thatfollow this document.FIGURE 3ANGLE OF PROJECTION SYMBOLON DUAL DIMENSIONED DRAWINGS6. InterchangeabilityInterchangeability of parts, functionally, physically, or both, is dependent upon thedegree of round-off accuracy used in converting an inch value to a metric value or a metric val
29、ue to an inchvalue with the resultant placed on a drawing. For conversion principles, see ANSI IEEE/ASTM SI 10, Standardfor Use of the International System of Units (SI): The Modern Metric System, and SAE TSB 003, Rules for SAEUse of SI (Metric) Units. Where considered necessary, dual dimensioned dr
30、awings should identify the refereedimensional units to assure acceptability of product and repeatability of inspection practices.7. Drawing ApplicationWith the addition of a title block and applicable notes, Figure 3 illustrates a typical dualdimensioned drawing.COPYRIGHT Society of Automotive Engin
31、eers, Inc.Licensed by Information Handling ServicesSAE J390 Revised MAY1999-5-8. Notes8.1 Marginal IndiciaThe change bar (l) located in the left margin is for the convenience of the user in locatingareas where technical revisions have been made to the previous issue of the report. An (R) symbol to t
32、he leftof the document title indicates a complete revision of the report.PREPARED BY THE SAE DRAWING STANDARDS COMMITTEE AND METRIC ADVISORY COMMITTEECOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J390 Revised MAY1999RationaleNot applicable.Relationship o
33、f SAE Standard to ISO StandardNot applicable.ApplicationThis document covers a dual dimensioning practice that provides both U.S. customary inch-pound units and SI metric units for all dimensions on the field of the drawing. The scope does notinclude the “chart method”whereby drawings are dimensione
34、d only in SI unitswith conversions toinch-pound units provided in chart form (usually computer-generated) on the drawing. Reference SectionSAE TSB 003Rules for SAE Use of SI (Metric) UnitsANSI Y14.5Dimensioning and Tolerancing for Engineering DrawingsIEEE/ASTM SI10Standard for Use of the International System of Units (SI): The Modern Metric SystemDeveloped by the SAE Drawing Standards Committee and Metric Advisory CommitteeCOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling Services
