Surface Profile with NO datum reference frame

[jammin7800]

Typically, when we DO see datums specified on a surface profile callout, that tells us to set the part up to datums and measure the surface relative to those datums. No best-fitting allowed.

Also typically, if we DO NOT see a datum reference frame on the tolerance, that tells us we are allowed to best fit that surface onto its nominal shape, using all 6 DOF.

I have a situation where a surface profile tolerance is on a print with NO DRF. The customer is telling me that it is IMPLIED that this is wrt datums, even though none are specified.

Further, he claims this is part of his company's specs. I looked at the spec, this situation isn't covered. But the spec does reference ASME 14.5M-1994. So I looked at the ASME spec. I couldn't find it in there either.

So my question is this --- what does ASME say about surface profile tolerances that do not reference datums? Is it IMPLIED that datums are specified, or does no DRF mean best-fitting is allowed?

 

[btrueblood]

recommend you RF this post/thread, and repost in forum:

Engineering Methods/>Drafting Standards, GD&T & Tolerance Analysis