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Datum Identifiers
What is the reason for not use I, O and Q as datum identifiers?

5 months ago
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DennisUnfollow Follow Dennis
Dennis Schwartz • Wilson,

The reason is that I could be confused with 1, and O and Q could be confused with each other or confused with a 0.
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WilsonUnfollow Follow Wilson
Wilson Alvares • That is what I was thinking. However, I thought there were other more serious reasons. I have already used it but now I'm gonna avoid that.

Thank you Dennis!
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RafaelUnfollow Follow Rafael
Rafael Rivera • Other Letter Exceptions are:

Datum Feature Letter Exception: I, O, and Q
ASME Y14.5M-1994 Paragraph 3.3.2

View Letter Exception: I, O, Q, S, X, and Z
ASME Y14.3-2003 Page 7, Paragraph 1.7.3

Section Letter Exception: I, O, Q, S, X, and Z
ASME Y14.3-2003 Page 15, Paragraph 3.2.2

Revision Letter Exception: I, O, Q, S, X, and Z
ASME Y14.35M-1997 Paragraph 5.1

For the reason Dennis mentioned.
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John
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John Miles • Also in the Mandatory Appendix I of ASME Y14.41-2012 it states that I,O, Q, S, X, Y, & Z should not be used for views on a 3D model. (I,O,Q,S,Z to comply with 14.3 and Y for any confusion to the Y in a displayed model coordinate system)

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