On Wed, 11 Apr 2012 10:37:03 +1000, F Murtz
wrote:

Wild_Bill wrote:
Roasting speeds are generally attained by using a worm gear reduction.

Don't you still have to cut a gear? and the worm on a lathe?

A good worm gear is somewhat concave in the middle -- exactly what you
get when you cut it with a tap mounted in the spindle, with the gear
blank freewheeling on some kind of fixture. I have used a lathe, with
the tap in a collet (or maybe in my 4-jaw; it was a long time ago, and
I forget), and the gear blank turning free on a simple spindle held in
my milling attachment. There are other ways to rig it if you don't
have a milling attachment.

The worm is a simple thread-cutting job in the lathe. The set will
match quite well but it's not something you'd want to use for a real
high-torque job.

--
Ed Huntress