Thank you both for the information!
I have the knurler made by Sherline for the Sherline lathe. It comes with a single pair of medium knurls (30 degree spiral knurls with a 90 degree tooth angle at 25 TPI) for making diamond knurls, but I wanted to order straight fine knurls for making thumbscrews.


The difficulty that I'm having is choosing the best pitch and tooth angle. Sherline offers straight tooth knurls in 16, 20, 25, 30, 32, 35, 40, 41, and 47 TPI with a 90 degree tooth angle, and 35, 50, 53, 60, and 80 TPI with a 70 degree tooth angle. I'm guessing that for smaller parts a fine straight knurl would be around 40 TPI. I was wondering if there is any kind of guideline for determining the best pitch for a given diameter. I can count the teeth from a 10-32 socket head to get extra fine.

I'm thinking that I might want something more course for 3/8" to 1/2" diameter.