Referencing a Datum feature of size multiple times
Referencing a Datum feature of size multiple times
(OP)
I have a drawing with multiple pages. Datum A is defined as a feature of size on page 1. On page 2 we dimension another feature to the center plane of datum A. The center plane of datum A is represented by a centerline in this view, but because the centerline can be tied to multiple features shown in the view, it is necessary to define it as the center plane of datum A. How should this be accomplished?
I understand that ASME 14.5 forbids a datum flag to be attached to a centerline. This leaves only the use of a note or changing the dimension scheme. If a note can be used, what is the proper syntax?
I understand that ASME 14.5 forbids a datum flag to be attached to a centerline. This leaves only the use of a note or changing the dimension scheme. If a note can be used, what is the proper syntax?





RE: Referencing a Datum feature of size multiple times
That being said, there really isn't any reason to reference a datum twice on the same drawing. As long as it is clearly defined on a veiw it should be enough. There is no reason that you would need to be concerned about someone misinterpreting which feature to dimension to as long as you reference datum A in your FCF.
RE: Referencing a Datum feature of size multiple times
RE: Referencing a Datum feature of size multiple times
ewh, I originally considered a "centerline", but although the line type used would be a centerline, the actual feature represented is a plane. It appears as a line because itexists in a single dimension in the view.
I'm inclined to go with the note, but it would be nice to know if there is some precident for this situation in the official ASME universe.
Thanks for the help so far.
RE: Referencing a Datum feature of size multiple times
WHEN IN DOUBT, SPELL IT OUT.
RE: Referencing a Datum feature of size multiple times
Instead of "CENTERLINE DATUM A" why don't you just use "CENTERPLANE DATUM A"? It is not ambiguous, and a centerline font would be appropriate.
RE: Referencing a Datum feature of size multiple times
How about just "Datum plane A"?
RE: Referencing a Datum feature of size multiple times
RE: Referencing a Datum feature of size multiple times
RE: Referencing a Datum feature of size multiple times
RE: Referencing a Datum feature of size multiple times
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Referencing a Datum feature of size multiple times
i.e. For datum A, do not use View A or Section A, etc.
Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 10-27-06)
RE: Referencing a Datum feature of size multiple times
RE: Referencing a Datum feature of size multiple times
And if it AINT in a standard, just something to be debated.
RE: Referencing a Datum feature of size multiple times
Datums went from A, as ringman said because of the box we assumed they wouldn't be easily confused.
At my new place, in the States, we only use each letter once be it for view, section or datum, and we start at A. (I got in trouble with the checker for XX my first week and haven't repeated it!)