Is this a valid DRF?

[[Ja...]]

I have a position called out as [Ø|.005|A|B]. This DRF does not lock translation in the cylinder axis direction.

When/why is/isn't it allowed to make a callout to an incomplete DRF?

[[Br...]]

A DRF only needs to constrain the degrees of freedom necessary. Where is this diameter located on the part? Depending on its relationship to the datums, a tertiary datum may be unnecessary.

Drawings do need to be fully defined, but if that particular feature has its form, size, orientation, and location defined within the drawing without need of a tertiary datum, then thats all you need. Datum features for instance, often do not need fully constrained datum reference frames because they make up the datum reference frame.(gotta start somewhere.) In your example, Datum Feature A being the primary datum only needs form controlled(most likely flatness will do.), Then Datum B will need size, form, orientation and location back to A controlled. A Size on the diameter and position tolerance back to A would control all of that.

[[Ja...]]

Brett,

The diameter in question is at the end of -B- (thru hole). It is in fact a datum that is then used in other FCF's.

Thanks for clarifying for me.