Thanks everyone! That made things much more clear, especially that long post from axym.
Pmarc, I haven't had a chance to review your new example yet, but I will soon.
I'm eager to get a more firm grasp on GD&T and whip our inspection department into shape.
I'm gonna have a talk with our cmm...
Pmarc,
Please disregard the first example, I understand how the best-fitting is allowed when the datum feature is referenced at MMC/MMB in Figure 4-6.
My second example (sketch) is like what I'm dealing with (datums referenced at RFS).
So what you're essentially saying in your second post is...
Axym,
Thanks, that was the same conclusion I kept arriving at after pouring over ASME Y14.5.
We have many customer supplied drawings where datum features have TP call-outs (such as the Datum C in my example).
What would the meaning of these call-outs be, since by definition the position of the...
Sorry for the lack of clarification.
I am not talking about the least squared algorithm vs actual mating envelope as Belanger describes.
Axym is on the right track, but let me clarify.
Please see the attached picture.
Datum C has a TP callout to 0.5 and Datum C is the tertiary datum in the TP...
I am trying to find a justification in ASME Y14.5 for doing best - fit alignments when there is a true position on a datum feature.
For example: a simple disk with a face as datum A, OD as datum B, a slot as datum C. (Ie. ASME Y14.5-1994 Figure 4-6)
A true position call out on datum C should...
