"Robert Swinney" wrote in message
...
A general expression for the size of a rod for threading is: " Major
diameter minus (.10825 / # of threads per inch)"

In the case of a 3/4 - 16 it would be: 0.750 - (.10825 / 16) = 0.7432

This would "cut" a class 3A thread, approximately. It might also result
in
die damage if cutting hard material such as stainless or etc. Check
Machinery's Handbook for tables of allowances and max - min major
diameters
for classes of threads.

Bob Swinney


Well, lets say it *could* yield a class three thread, but that has little to
do with the major diameter. Class of fit is controlled by the pitch
diameter, which, from class to class, is very close to identical, but not
necessarily identical. Each of the classes can share the same major
diameter, so you can't discern a class fit by that measurement. As you
and I have discussed before, the critical dimensions on screw threads are
always the pitch diameters, although all features must be within specs for a
proper thread.

Harold