Bill Darby wrote:

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".

Bill, you have sadi this many times and now I wonder if we both mean the
same thing by "major diameter". I mean the mesurement I get if I close
a flat faced micrometer over the outside of a male thread having removed
any burrs if present. What do you mean?

I ask because I understand that the only 1/4" thread with a full 0.2500"
o.d. would be one with a sharp V-topped thread. Any comercial 1/4"
thread I have measured has always been rather less than 0.2500 o.d.,
typically by about 1/8 of the nominal thread depth.

Also, any thread I have single pointed has always needed to be cut a
little deeper to fit than you indicate, assuming I understand you
correctly. I would like to understand this better.

Ted