GD and T General question

[[Ma...]]

Ok, I realize this is probably a simple one but why can't you call-out TP of Datum C using FCF ABC? I know you can't but how is the part fully constrained if its only called back to AB?

[[DW...]]

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 Can you share a snippet of a drawing or elaborate? Without knowing what type of features A, B, and C are this question is hard/impossible to answer. 

[[Jo...]]

True positions don't have to fully constrain a part.  You can TP to one datum if youd like (You get only perpendicularity, but its legal).  The positions apply with whatever constraints are offered. 

 

Since datums consume constraints as they are available, you need more information than just ABC to help more. 

 

 

Edited Wednesday at 07:00 PM

[[Ma...]]

[[Ma...]]

Datum C is just for stopping rotation - it's like using bestfit rotation. Nothing bad here. You still have to have correct distance from B origin.

[[Ma...]]

But wouldn't the proper way to set that up be TP of C to AB and then use Best fit TP Callout, using the feature in the TP callout as a Datum seems wrong.