The TPI between the two standards (American and metric) - in this
case - are very close resulting in very little thread stock being
removed. In the short thread length involved here (about 1/2-inch) and
the threads are not rendered to nothing more than bumps.However, at
longer thread lengths it well could be a problem, but not at the
1/2-inch distance we are talking about here.

Again I ask, have you actually tried this?

I have used this method numerous times for myself and friends and I
have never experienced any kind of failures or problems in doing so.


Yes. and I would not trust the end result to any kind of load, it is fine
for a cable connection but certainly not as a method of retaining a mobile
antenna at speed!

Perhaps the difference is in the die, and the length of thread in the die.
The thicker the die the truer the thread will be and the more pronounced the
removal of the metric thread.

The OP was suggesting a 'die nut' which will be quite thick and I suspect
would produce results similar to those I have found.

Jeff