Been wondering if I could get a fairly accurate depth of thread
measurment with only a single wire and a mic.
*****************************

So I took a new 1/2" 13 bolt and miced it. The measurnent of the major
diameter was .489"

I miced it again with a .040" drill bit inserted in the thread. The
measurnent was .496"

In order to balance that reading I subtracted half the major diameter of
the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 =
..503"

So I now had the equivalent to a 3 wire reading. [IE .503"] So the
sharp depth diameter reading would be 3 times the .040" drill diameter
less or .503"- 3 * .040" = .383"

The pitch diameter would be one pitch height greater or .383" +
1/13*.86603" = .4496"

This .4496" pitch diameter falls nicely into the pitch diameter range
of a class 3A thread.
******************************
Bill

May seem complicated to do but you need no special kit, only two hands,
and once you figure out the mechanics of it, it is easy and I would
guess that the accuracy, while not as good as the proper three wires, it
could serve most quite well.

Bill

(Hoping I didn't foul up my numbers)