Need to measure some threaded holes 1/4-28 UNJF.
Anyone know where I can find plugs for this thread to check location?
Consider this, when the fastener tightens in the thread it is the flanks of the thread that contact. This contact tends to force the fastener into the center of the pitch diameter(like a taper). The minor dia does not contact. Depending on your method for thread cutting...I believe that you can actually machine a thread that is off center to the minor diameter!!
The minor diameter is basically the tap drill size and depending on what percentage of thread you require...or whether you are using a roll or cut tap...or whether you are machining threads oversize for plating etc., the minor dia is simply the clearance size for your thread cutting tool.
