ASME Standards for the Revision of Engineering Drawings
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 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 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
We use numbered Revs for prototype drawings, i.e. Rev 1, Rev 2 etc. When we are ready to release for production we change to letters i.e. Rev A, Release for Production, Rev B, Rev C etc. Sometimes at Rev A we still change things. Do changes at Rev A require a change letter symbol designation? Triangle/circle A to locate the change? Do the changes get recorded in the revision block?
In general, revisions numbers / versions 1 and 2 are for little changes and things in work, while revision letters are for major, released changes. When you make major changes, issue a formal revision letter change for the new drawing.Helpful 1
Should engineering drawings be numbered as Rev 1 or Rev 01?
01, because you can end up with 28 revisions.Helpful 2
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.Helpful 1