ASME Standards for the Revision of Engineering Drawings

Updated on January 8, 2018
tamarawilhite profile image

Tamara Wilhite is a technical writer, industrial engineer, mother of two, and published sci-fi and horror author.


American Society of Mechanical Engineers standard ASME Y14.35M was issued in 1997 to describe the ASME approved format for tracking revisions and other changes to engineering drawings. ASME Y14.35M was reaffirmed in 2003, and no changes were made at that time. It updated to the name ASME Y14.35 in 2014.

What does ASME Std Y14.35 mandate?

ASME has issued standards for the proper documentation of drawing revisions.
ASME has issued standards for the proper documentation of drawing revisions. | Source

ASME Y14.35M Standard

ASME Y14.35M and the later ASME Y14.35 standard allows for changes to be made to drawings by adding and crossing out information on a drawing or by creating a new drawing revision.

The ASME drawing standards state that new drawings can be recorded as a new revision letter or as a new drawing number that supersedes the old one. The replaced drawing will be modified to note “replaced with change by drawing 1234567”. This ensures configuration management and product verification is handled correctly.

The first version of a drawing is identified by a revision dash “-“. After that, revision letters are used. Revision letters can be a single letter up to multiple letters.

All letters can be used as revision letters except I, O, Q, S, X and Z. These letters are not allowed because they can be mistaken for numbers or for other letters. For example, a revision letter I can be mistaken for a 1 while an S can be mistaken for a 5. Revision letters must also be uppercase, to minimize confusion between a lowercase "l" and "1" and "I".

After the end of the revision letter sequence is used up, the next letter is added to the end. Revision letter Y is followed by revision AA. Revision AY is followed by BA. Revision DY is followed EA.

However, revision letters are not allowed to exceed two characters, so there is no revision greater than YY. At this point, you should issue a new drawing number.

Revision columns are located in the upper right corner or next to drawing the title block. Revision columns include the revision letter of the drawing, a short description of the changes made between this revision and the prior one, and the date the revision was made or the revised drawing was approved. Revision columns frequently include the drafter who made the latest revisions.

ASME standards require parts to be labeled with the part number and revision letter per their manufacturing drawings.
ASME standards require parts to be labeled with the part number and revision letter per their manufacturing drawings. | Source

Related Standards

ASME standard Y14.24 gives readers a list of when ASME engineering drawing standards like ASME Y14.35 apply. ASME Y14.1 defines the acceptable form of the revision history block.

ASME Y14.1 gives the ASME standard size and format used in engineering drawings.

ASME Y14.2 outlines the accepted line conventions and lettering used on engineering drawings. ASME Y14.3M describes the accepted forms of single, multiple and sectional views used on engineering drawings.

ASME Y14.100 provides a list of standard engineering drawing practices recommended by the ASME. Depending on the customer or project, other ASME or ISO standards may also be required. And ASME drawing standards do not cover documentation control or configuration management at all.

Questions & Answers

  • I want to know if a particular piece has 4 drawings associated to it and you make a change on one of the drawings, shouldn't all the drawings be changed to the same rev level? Meaning if they were Rev A then they all would change to Rev B?

    No. Suppose the top level part is 1234567 rev A, and the child drawings are 23456 rev A and 78901 rev A. If 78901 rev A becomes rev B, the top level assembly needs to be updated to say if rev B is allowed on the parts list, but the related 23456 rev A stays rev A.

    If changing one drawing changes everything that's associated with it, you would never stop churning out the updates.

  • When an engineering drawing is revised to be completely different than the original by different engineers than the original drafter and checker, does that information in the title block change? Can the information in the title block ever be revised if it is unrepresentative of the revised work?

    If car name X is radically revised in revision B, they could create revision A with rev B and still call it the same car and drawing number. If they turn a car into a plane, it should be a new drawing number.

  • Should engineering drawings be numbered as Rev 1 or Rev 01?

    01, because you can end up with 28 revisions.

  • Is the ASME standard rev1 or should it be REV1 when naming the file?

    I've seen it written as both "Rev" and "REV".

  • A child drawing was updated to a later revision - does the parent drawing need a revision update? The bill of material does identify the child item but no rev.

    If the child item is still compatible with the parent part, no, you don't need to update it. If rev A doesn't fit but rev B does, specify that in the bill of materials.


Submit a Comment
  • tamarawilhite profile imageAUTHOR

    Tamara Wilhite 

    5 months ago from Fort Worth, Texas

    From what I have observed, the same revision letter system applies whether it is test plans or wiring diagrams.

  • profile image

    Tim Marion 

    5 months ago

    Does this also apply to the labelling of electrical wiring in wiring diagrams where the use of lowercase and uppercase lettering is used?

  • Garry Reed profile image

    Garry Reed 

    14 months ago from Dallas/Fort Worth, Texas

    Interesting. I was an on-the-board drafter for many years back in the olden days and all changes to defense system drawings where executed by ERs (Engineering Requests) and EOs (Engineering Orders) if my poor old brain remembers.

    Even during modern times as a tech writer and logistics specialist doing all work via computer programs I had to stay abreast of drawing changes and pending changes, and as a logistics engineer even recommended some of those changes myself.

  • tamarawilhite profile imageAUTHOR

    Tamara Wilhite 

    14 months ago from Fort Worth, Texas

    I don't know how to handle documention within SAP.

  • profile image


    14 months ago

    I have a question: Can a description be changed in SAP system only adding dimensions to description without creating an ECO. No change is being made to the drawing or title block. Drawing title: Label, description in SAP- Label. When looking for a label drawing in the system( shouldn't they have dimensions in the description to make it easier to locate what your looking for? Question is: Can you add to the description without writing and ECO on an active part number.

  • tamarawilhite profile imageAUTHOR

    Tamara Wilhite 

    24 months ago from Fort Worth, Texas

    Update the most recent released drawing to the next revision letter.

  • profile image

    James R Dunn 

    24 months ago

    I have a question about revisions. I recently found a drawing from my company that has the same revision letter used twice. What is the proper way to handle this mistake?

  • tamarawilhite profile imageAUTHOR

    Tamara Wilhite 

    2 years ago from Fort Worth, Texas

    MZ1 Form what I've seen, they use the same symbols for drawings. However, concentricity and symmetry differ. ISO uses geometric tolerancing and doesn't recognize that used by the ASME standards.

  • profile image


    2 years ago

    Hello Tamara

    Our company is certified lately to AS9100 standard

    I’m looking for a linkage between:

    ASME Y14.35M rules



    I mean where should I find the ASME Y14.35M rules in AS9100 ?


  • tamarawilhite profile imageAUTHOR

    Tamara Wilhite 

    3 years ago from Fort Worth, Texas

    The "M" refers to metric version of standards like the older version of ASME Y14.34M; the "M" disappears when metric and non-metric standards are consolidated.

  • Steel Engineer profile image

    Steel Engineer 

    6 years ago from Kiev, Ukraine

    Worthwhile read. Thanks for sharing this.


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