Never buy another worm.

I went home this weekend with a dire need to hob some gears. It
was so easy, I couldn't believe it.
I made a holder to fit my quick change out of 1/2 x 3/4 keystock
and proceeded to turn out a 69 tooth, 1/4-20 worm gear. Seriously,
starting from scratch and screwing up once it took me 15 minutes.
I found out that you can't use the 2 flute "gun" taps. They don't
stay in the cut long enough to feed the blank. The cheap 4 flute
generic type works best. I think someone reccomended the spiral
style
and that would be even better. I ran the tap about 500 rpm feeding
about .010" per rev of the blank, supported the outboard end of the
tap by just jamming it into a peice of brass held in the tailstock.
The cutting stops when you get to the root.
I used a piece of silicon bronze that only had a few tho' to go
for
the proper blank size. I put a red dot on the blank so I could watch
for the proper motion.
So never throw those old broken taps away either, they make great
gear hobbers.
I will post pictures tomorrow.