Hi. I'm new to this forumn.
We sometimes encounter the minor diameter of form tapped threads falling just over the the upper limit of the thread spec. This causes the thread quality to be a "judgement" call. Some operators claim there are specs specifically for form tapping, but I have yet to find anything like that & they have yet to produce them. Does anyone no of any such standards or specs? I'd like to eliminate the "judgement" part of the quality question from the equation for good.
You may have already found the answer you are looking for but here goes.
There is a differant spec for rollform diameters. You can find it in the Machinist Handbook. It will give you the specs for classes 1A thru 3A for maximum, minor diameter useing pin gages. Hope this helps.