On Jan 12, 7:48 am, Lew Hartswick wrote:
clare at snyder.on.ca wrote:
I think it is also used on some electronics devices - the thread on
some control stems (potentiometers) is 18 TPI from what I remember - I
know neither UNC or UNF nuts fit, and nor do metric standards.

I worked in the electronic field for nearly 60 years and never saw
a potentiometer with a coarse thread. The 3/8 ones were 32 and the
"modern" 1/4 are 40. The damn metric ones I don't know about. :-)
...lew...

A few months ago I had to make some custom mountings for
potentiometers and encoders, and I had to buy a special 3/8"-32 tap
for the stem. It was aweful to tap since it was so large but such a
fine thread. Took me 4 tries to get it right.