Thread Diameter as a Datum

OmarEn

Involved In Discussions
#1
Hello guys.

I have a question of how to threat a thread diameter called out as a Datum.
Attached is a portion of the drawing in question.
This part has 4 extremities with threaded nuts called out as a Datum . 4 of them are primary Datum. rest of them are secondary.
bottom line here is that since they are Datum, I think It means It´s not necessary for them to lie at its nominal position since that would not be possible. I mean, It is not possible to manufacture a part that lies perfectly in Its nominal position. if this feature does not have a position tolerance but is a datum, we are allowed to drive that feature to its nominal position so we can immobilize the part.

Am I right?

Thanks in advance.
 

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Ron Rompen

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#2
I dealt with much the same problem (on the same type of part) supplying Chrysler. What we agreed to in the end was that a fixture was built to accept the threaded connectors. The top 1/4 or so of the 'mating part' was removed, so that we could observe whether or not the threaded fitting actually seated in position.
This fixture was also used to verify other positional and profile callouts for fasteners, bends, etc.
Hope this is of some help to you
 
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