Threadforming

Yesterday I was doing a bit of testing regarding threaded holes for 5mm screws in Delrin (aka POM, acetal) and found that a 3/16" drill bit drilled the perfect size hole that when given a slight nudge, a 5mm screw would enter the hole and form its own threads in the plastic along the way. The threads formed in this manner were actually giving me a better, more solid grip than I was achieving through traditional tapping.

Well, last night after having spent a couple painstaking hours tapping...

Threadforming