The shaft to be threaded should be turned down to dims re the formula: Nominal diameter - (.10825 /
# thds per inch) For a 1/2-13 that would be: 1/2 - (.10825 / 13 ) = 0.491 in.

Bob Swinney
wrote in message m...
I wish to thread a 1/2 shaft to 1/2 13 what should be the major dia. of the
shaft be.