"Stealth Pilot" wrote in message
...

I'm restoring an ancient Myford ML7 for use in model engine
building.(K5973)

The spindle and whitemetal bearings are in very good condition but the
gears in the headstock are all shot.
The gears are a mixture of cast iron, mazak and bronze.
The cast iron gears seem to have stood up to the 50 years of use quite
well.
The mazak gears show some wear. The bronze gear teeth are almost worn
to a feather.
This would all point to cast iron being a better material for the
replacement gears.

My Hercus (south bend clone) is all cast iron gears and shows almost
no wear on the gear train teeth. again this points to cast iron being
a better gear material in this type of application.

What is the general consensus of opinion on the materials for making
lathe gear wheels?

I have bars of meehanite which are big enough to give me most wheels.
Of the various cast irons is meehanite a good material for making long
lasting gears?

The gears for the myford and the hercus dont match at all, even in
similar diameters. this points to one set being 20 degree pitch
angle(PA) and one set being 14.5 degree PA.
does anyone know what PA the myford gears were? even after reading
Ivan Laws book on gears and gear cutting I still cant look at a gear
in my hand and work out just by looking at it what the pressure angle
would be. are the teeth of 14 and a half degree gears fatter or
thinner than similar gear diameter 20 degree pressure angle gears?

a 65 tooth bull wheel seems near useless for detent style dividing.
has anyone rebuilt a myford bullwheel in some other tooth size that
has proven to still be adequate?

so many questions :-)

If I surrender I can still buy replacement gears from myford but
cutting my replacement gears would be quite cool.

What is your capability for cutting gears? Are you using gear cutters on a
mill?

Having done that, commercially and with good equipment, I'd say you're in
for more work that it's worth -- in money, at least. If you enjoy the
work...well, you enjoy the work. Then it doesn't matter.

As for materials, I'll leave that to others with more experience. My
experience with highly-loaded bronze gears starts and stops with a '57 Alfa
Romeo engine that had a bronze distributor-drive gear. My '58 had a steel
gear. The bronze wore out in a hurry; the steel never wore out when I had
it, and that was a high-rpm race engine. But there are many different grades
of bronze, and their performance in high-load-bearing applications also
varies widely. I wouldn't attempt to generalize.

--
Ed Huntress