On Wed, 22 Oct 2008 15:07:32 -0700, Jim Stewart
wrote:

I need a reality check. I constructed this
7/8-20 UNEF Class 2A thread from the data I
found in the Machinery's Handbook. I can't
believe that the minor diameter lops so much
off of the lower part of the form. Is this
right?

http://www.grumpyoldgeek.com/images/UNEF_thread.jpg
==========
While you will need three hands to use it, invest in a three wire
thread gage set. [Don't loose the instruction/cheat sheet that
comes with it.] Hint: use a wad of modeling clay to hold the
three wires in position as you measure the pitch diameter of the
thread.

http://www.vankeuren.com/tmo.aspx

Most any mill supply should have in stock. For an example see
http://www.use-enco.com/CGI/INPDFF?P...MITEM=619-3127
left hand side about 1/3 down -- thread measuring wire sets.



Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).