I was building a knife sharpener today and used a ground hardened rod and figured it would be nice to have a threaded end.
So being lazy I didn'd anneal the end and started threading it.
What the heck....... the good file gave a little scatch on the end.
Well............3 carbide inserts ( they are indexable and have three cutting edges), 2 hours of machining, more crackling and poping of material then I ever experienced, and finaly had a 3/8"- 40 thread - 1 1/2" long.
Happy i didn't try 16 or 24 tpi.
Guess one just never pays attention to his owne advice!
RICH