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Switching form rev. numbers to letters, which letters to use

Switching form rev. numbers to letters, which letters to use

Switching form rev. numbers to letters, which letters to use

My company is now switching from revision numbers to revision letters on our engineering documents. Numbers will now be used to track design revisions before documents are released. After they are released we will use letters to track revisions. My question is, are all the letters of the alphabet accepted for revisions? I was told that some might not be accepted. If so does any one know why they are not used?

RE: Switching form rev. numbers to letters, which letters to use

You should not use I, O or Q.  The reason is they might look too similar to 1 and 0.

"The attempt and not the deed confounds us."

RE: Switching form rev. numbers to letters, which letters to use

ASME Y14.35M-1997, "Revision of Engineering Drawings and Associated Documents" states the following for the the use of revision letters:

"5.1 Revision Letters
Upper case letters shall be used in sequence beginning with A and omitting letters "I," "O," "Q," "S," "X," and "Z'. When the single letters have been exhausted, the revisions following "Y" shall be "AA," "AB" through "AY". Should "AA" to "AY" be exhausted, the next sequence shall be "BA," "BB," etc. Revision letters shall not exceed two characters. Initial issue of a drawing does not constitute need for a revision letter and may be indicated by the use of a - (dash).symbol."

Hope this helps


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