Dimensioning and Tolerancing: Engineering Drawing and Related Documentation Practices.
Contents:
Section 1 Scope, Definitions, and General Dimensioning
Section 2 General Tolerancing and Related Principles
Section 3 Symbology
Section 4 Datum Reference Frames
Section 5 Tolerances of Form
Section 6 Tolerances of Orientation
Section 7 Tolerances of Location
Section 8 Tolerances of Profile
Section 9 Tolerances of Runout
Nonmandatory Appendices
Index
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 mating 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 feature 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 manufacturing, 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.
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 invention 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.
Book Details:
⏩Author: The American Society of Mechanical Engineers
⏩Copyright © 2009 by
THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS
⏩Language: English
⏩Pages: 227
⏩Size: 12.2 MB
⏩Format: PDF
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