ASME 2009

AN INTERNATIONAL STANDARD
ASME Y14.5-2009
[Revision of ASME Y14.5M-1994 (R2004)]
Dimensioning
and Tolerancing
Engineering Drawing and Related
Documentation Practices
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Dimensioning and
Tolerancing
Engineering Drawing and Related
Documentation Practices
AN INTERNATIONAL STANDARD
[Revision of ASME Y14.5M-1994 (R2004)]
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CONTENTS
Foreword  .............................................................................................................................................................................. vi
Committee Roster ................................................................................................................................................................ viii
Correspondence With the Y14 Committee  ...................................................................................................................... ix
Section 1 Scope, Definitions, and General Dimensioning   ...................................................................................... 1
1.1 Scope  ................................................................................................................................................................ 1
1.2 References  ....................................................................................................................................................... 1
1.3 Definitions  ...................................................................................................................................................... 2
1.4  Fundamental Rules  ........................................................................................................................................ 7
1.5 Units of Measure  ............................................................................................................................................ 8
1.6  Types of Dimensioning  ................................................................................................................................. 9
1.7  Application of Dimensions  .......................................................................................................................... 10
1.8  Dimensioning Features  ................................................................................................................................. 13
1.9  Location of Features  ...................................................................................................................................... 20
Section 2 General Tolerancing and Related Principles   .......................................................................................... 24
2.1 General  ............................................................................................................................................................ 24
2.2 Direct Tolerancing Methods  ......................................................................................................................... 24
2.3 Tolerance Expression  ..................................................................................................................................... 25
2.4  Interpretation of Limits  ................................................................................................................................. 26
2.5  Single Limits  ................................................................................................................................................... 26
2.6  Tolerance Accumulation  ............................................................................................................................... 26
2.7  Limits of Size .................................................................................................................................................... 27
2.8  Applicability of Modifiers on Geometric Tolerance Values and Datum Feature References  ............. 29
2.9  Screw Threads  ................................................................................................................................................ 31
2.10  Gears and Splines  .......................................................................................................................................... 31
2.11  Boundary Conditions  .................................................................................................................................... 31
2.12  Angular Surfaces  ........................................................................................................................................... 31
2.13  Conical Tapers  ................................................................................................................................................ 35
2.14  Flat Tapers  ....................................................................................................................................................... 35
2.15  Radius  .............................................................................................................................................................. 36
2.16  Tangent Plane  ................................................................................................................................................. 36
2.17  Statistical Tolerancing  ................................................................................................................................... 36
Section 3 Symbology   .............................................................................................................................................. 38
3.1 General  ............................................................................................................................................................ 38
3.2 Use of Notes to Supplement Symbols  ........................................................................................................ 38
3.3 Symbol Construction  ..................................................................................................................................... 38
3.4  Feature Control Frame Symbols  .................................................................................................................. 44
3.5  Feature Control Frame Placement  ............................................................................................................... 46
3.6  Definition of the Tolerance Zone  ................................................................................................................. 46
3.7  Tabulated Tolerances  ..................................................................................................................................... 46
Section 4 Datum Reference Frames   ........................................................................................................................  48
4.1 General  ............................................................................................................................................................ 48
4.2  Degrees of Freedom  ....................................................................................................................................... 48
4.3  Degrees of Freedom Constrained by Primary Datum Features
 Regardless of Material Boundary  ............................................................................................................ 48
4.4  Constraining Degrees of Freedom of a Part  ............................................................................................... 48
4.5  Datum Feature Simulator  ............................................................................................................................. 53
4.6  Theoretical and Physical Application of Datum Feature Simulators  ..................................................... 53
4.7 Datum Reference Frame  ............................................................................................................................... 53
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4.8  Datum Features  .............................................................................................................................................. 57
4.9  Datum Feature Controls  ............................................................................................................................... 58
4.10  Specifying Datum Features in an Order of Precedence  ........................................................................... 58
4.11  Establishing Datums  ..................................................................................................................................... 59
4.12  Multiple Datum Features  ............................................................................................................................. 65
4.13  Mathematically Defined Surface  ................................................................................................................. 69
4.14  Multiple Datum Reference Frames  ............................................................................................................. 69
4.15  Functional Datum Features  .......................................................................................................................... 69
4.16  Rotational Constraint About a Datum Axis or Point  ................................................................................ 70
4.17  Application of MMB, LMB, and RMB to Irregular Features of Size  ...................................................... 74
4.18  Datum Feature Selection Practical Application  ......................................................................................... 75
4.19  Simultaneous Requirements  ........................................................................................................................ 76
4.20  Restrained Condition  .................................................................................................................................... 79
4.21  Datum Reference Frame Identification  ...................................................................................................... 79
4.22  Customized Datum Reference Frame Construction  ................................................................................. 81
4.23  Application of a Customized Datum Reference Frame  ........................................................................... 81
4.24  Datum Targets  ................................................................................................................................................ 83
Section 5 Tolerances of Form   ..................................................................................................................................  91
5.1 General  ............................................................................................................................................................ 91
5.2  Form Control  .................................................................................................................................................. 91
5.3  Specifying Form Tolerances  ......................................................................................................................... 91
5.4  Form Tolerances  ............................................................................................................................................. 91
5.5  Application of Free-State Symbol  ................................................................................................................ 95
Section 6 Tolerances of Orientation   .......................................................................................................................  99
6.1 General  ............................................................................................................................................................ 99
6.2  Orientation Control  ....................................................................................................................................... 99
6.3  Orientation Symbols ...................................................................................................................................... 99
6.4  Specifying Orientation Tolerances  .............................................................................................................. 99
6.5  Tangent Plane  ................................................................................................................................................. 103
6.6  Alternative Practice  ....................................................................................................................................... 103
Section 7 Tolerances of Location   ............................................................................................................................  108
7.1 General  ............................................................................................................................................................ 108
7.2  Positional Tolerancing  ................................................................................................................................... 108
7.3  Positional Tolerancing Fundamentals: I  ..................................................................................................... 108
7.4  Positional Tolerancing Fundamentals: II  .................................................................................................... 119
7.5  Pattern Location  ............................................................................................................................................. 127
7.6  Coaxial Feature Controls  .............................................................................................................................. 148
7.7 Tolerancing for Symmetrical Relationships  ............................................................................................... 156
Section 8 Tolerances of Profile   ...............................................................................................................................  158
8.1 General  ............................................................................................................................................................ 158
8.2  Profile  .............................................................................................................................................................. 158
8.3  Tolerance Zone Boundaries  .......................................................................................................................... 158
8.4 Profile Applications  ....................................................................................................................................... 165
8.5 Material Condition and Boundary Condition Modifiers as
 Related to Profile Controls  ....................................................................................................................... 167
8.6 Composite Profile  .......................................................................................................................................... 167
8.7 Multiple Single-Segment Profile Tolerancing  ............................................................................................ 175
8.8 Combined Controls ......................................................................................................................................... 175
Section 9 Tolerances of Runout   ..............................................................................................................................  180
9.1 General  ............................................................................................................................................................ 180
9.2 Runout  ............................................................................................................................................................. 180
9.3 Runout Tolerance  ........................................................................................................................................... 180
9.4 Types of Runout Tolerances  ......................................................................................................................... 180
9.5 Application  ..................................................................................................................................................... 182
9.6 Specification  ................................................................................................................................................... 182
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Nonmandatory Appendices
A Principal Changes and Improvements  ................................................................................................. 185
B Formulas for Positional Tolerancing  ..................................................................................................... 191
C Form, Proportion, and Comparison of Symbols  .................................................................................. 194
D Former Practices  ...................................................................................................................................... 199
E Decision Diagrams for Geometric Control  .......................................................................................... 200
Index  .....................................................................................................................................................................  207
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FOREWORD
This issue is a revision of ASME Y14.5M-1994, Dimensioning and Tolerancing. The main object for this revision has
been to rearrange the material to better direct the thought process of the user when applying Geometric Dimensioning
and Tolerancing. The subject matter of Sections 1 through 4 remains the same as in the previous revision. Sections 5
and 6 were formerly titled “Tolerances of Location” and “Tolerances of Form, Profile, Orientation, and Runout.” The
new order following Section 4, Datums, is Section 5, Tolerances of Form; Section 6, Tolerances of Orientation; Section 7,
Tolerances of Location; Section 8, Tolerances of Profile; and Section 9, Tolerances of Runout. When applying GD&T the
first consideration is to establish a datum reference frame based on the function of the part in the assembly with its mat-
ing parts. After the datum reference frame is established, the form of the primary datum feature is controlled, followed
by the orientation and/or location of the secondary and tertiary datum features. After the datum features are related
relative to each other, the remaining features are controlled for orientation and location relative to the datum reference
framework. Further rearrangement has occurred within each section so that the basic concepts are presented first and
then the material builds to the more complex. The subcommittee believes this will aid the user of the Standard to better
understand the subject of Dimensioning and Tolerancing. 
Three new terms that are introduced are used only with datums. The terms are “maximum material boundary
(MMB),” “least material boundary (LMB),” and “regardless of material boundary (RMB).” These terms better describe
that there is a boundary defined when applying datums. MMB and LMB may be a maximum material or least material
boundary, respectively, or the applicable virtual condition. The MMB would be an actual maximum material boundary
if the tolerance (location or orientation) for that datum feature was zero at MMC. The LMB would be an actual least
material boundary if the tolerance (location or orientation) for that datum feature was zero at LMC. In the case of a fea-
ture of size as a primary datum feature, the MMB or LMB would be the actual maximum or least material boundary if
the form of the feature of size was controlled by Rule #1, or a zero at MMC or LMC straightness of the axis or flatness of
the center plane was applied. RMB indicates that the datum features apply at any boundary based on the actual size of
the feature and any geometric tolerance applied that together generate a unique boundary.
Since many major industries are becoming more global, resulting in the decentralization of design and manufactur-
ing, it is even more important that the design more precisely state the functional requirements. To accomplish this
it is becoming increasingly important that the use of geometric and dimensioning (GD&T) replace the former limit
dimensioning for form, orientation, location, and profile of part features. This revision contains paragraphs that give
a stronger admonition than in the past that the fully defined drawing should be dimensioned using GD&T with limit
dimensioning reserved primarily for the size dimensions for features of size. Additionally, recognizing the need to
automate the design, analysis, and measurement processes, and reduce the number of “view dependent tolerances,”
additional symbology has been introduced for some more common tolerancing practices.
Work on this issue began at a meeting in Sarasota, Florida in January 1994. Numerous deferred comments from the
public review for the previous revision, as well as proposals for revision and improvement from the subcommittee and
interested parties from the user community, were evaluated at subsequent semi-annual meetings.  The subcommittee
divided into working groups for several meetings and then reconvened as a subcommittee as a whole to review and
ensure the continuity of the revision.
Internationally, a new joint harmonization group formed in January 1993 was called the ISO/TC 3-10-57 JHG. The
object was to harmonize the work and principles among ISO/TC3 Surface Texture, ISO/TC 10 SC 5 Dimensioning and
Tolerancing, and ISO/TC 57 Measurement. The task of this group was to identify and suggest resolutions to problems
among the three disciplines. Many representatives of the ASME Y14.5 subcommittee participated in the meetings of this
group from September 1993 through June 1996. In Paris in June 1996 the ISO/TC 3-10-57 JHG became ISO/TC 213, and
the responsibilities of the three other ISO committees were transferred to ISO/TC 213. Representatives of the U.S. have
participated in all of the ISO/TC 213 meetings from June 1996 through January 1999. Because of difficulties, the U.S. was
not represented again until January 2006, and representation is now ongoing.
In the U.S., a similar committee was formed following the formation of ISO/TC 213 as a home for the U.S. TAG
(Technical Advisory Group) to ISO/TC 213 and also to serve as an advisory committee to the three U.S. committees
and subcommittees that are parallel to the ISO groups (Surface Texture B46, Dimensioning and Tolerancing Y14.5, and
Measurement B89). This new committee, called H213, was formed at a meeting in 1997 by representatives of the three
U.S. committees or subcommittees. H213 does not have responsibility for all three subjects as does the ISO committee,
but rather serves as an intermediary to identify and facilitate a resolution to problems that may exist among the three
disciplines as well as the home for the U.S. TAG.
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Suggestions for improvement of this Standard are welcome. They should be sent to The American Society of
Mechanical Engineers; Attn: Secretary, Y14 Standards Committee; Three Park Avenue, New York, NY 10016. 
This revision was approved as an American National Standard on February 6, 2009.
NOTE: The user’s attention is called to the possibility that compliance with this Standard may require use of an inven-
tion covered by patent rights.
By publication of this Standard, no position is taken with respect to the validity of any such claim(s) or of any patent
rights in connection therewith. If a patent holder has fi  led a statement of willingness to grant a license under these
rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license, then
details may be obtained from the standards developer.
Acknowledgments
P. J. McCuistion, Ohio University, created the illustrations for this Standard.
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ASME Y14 COMMITTEE
Engineering Drawing and Related Documentation Practices
(The following is the roster of the Committee at the time of approval of this Standard.)
STANDARDS COMMITTEE OFFICERS2893