I hope this is as simple as I think it is. I have a part the calls out the true position of a 5/16-18 ID threaded hole with MMC. I think that the MMC should come off of the minor diameter. Onr of the owners and the QA manager think it should come off of the pitch diameter. Other than the fact we don't have a good way to measure the pitch diameter in house I think they are wrong. What are the prevailing winds on minor or pitch for MMC on a ID threaded hole?
In most cases, the MMC should come off the pitch diameter, since that's the designed point of engagement.
This can be handled several ways:
1) Comment to measure manually, input PD, and use legacy dimensions with a formula in the tolerance field, based on input value (for some reason this field could not accept a formula in 2022, but I haven't had time to investigate).
2) If access is possible, all CMMs can measure pitch diameter directly, with a little creative coding (I normally perform the task this way)
3) just don't use MMC, but comment that this must be calculated manually, in cases of borderline failures
4) I have also seen programmers simply assume PD is nominal and add half the PD tolerance as a bonus (this is wrong)
