COMMON DATUM

[nry67]

My question concerns the "COMMON DATUM".
It is possible to create a "DATUM" bottom a control frame who calling 2 commons datums whose himself ?
See my picture to example.

 

[nry67]

I forgot the link ...

 

[KENAT]

I think you have a problem, what standards are you working to?

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MechNorth]

Where to start? First, under each FCF, the note "OVER DATUM A" and "OVER DATUM B" is incorrect and unnecessary. Second, perhaps shift the nuts further along the tube segments so that it isn't in the zones establishing Datum Feature A and Datum Feature B. At the same time, you need to show an offset chain line representing the segments for Datum Feature A and Datum Feature B. Third, it is maybe confusing to put the Datum Identifyer symbol on the FCF in THIS instance where the Datum Feature (A and B individually) is controlled back to the Datum established by Multiple Datum Features. I would put the Datum-A and Datum-B identifiers on the chain lines indicated in the second point.

Note, you may well get a lot of people opposed to the idea of controlling a Datum Feature back to a compound datum, but it is legal.

Jim Sykes, P.Eng, GDTP-S
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