Stealth Pilot wrote:

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.

comments welcome.
Stealth Pilot


Pressure Angle

Diametrical Pitch.

Myford gears are 20 DP, 14.5 PA. You won't need a full set of cutters,
just most of the set of eight.
There are a couple sources of replacement gears for Myfords, other
than the factory, and if you have to buy the set of cutters retail, the
replacement gears are a pretty attractive proposition.

If Hercus followed South Bend's lead (it is a licenced clone of South
Bend) then the gears are IIRC 18 DP(or 16 DP) 14.5 PA. These are
not a "preferred" size, and thus limit the number of sources.

Myford gears will be iron. Any other materials will be from some other
source,except the first gears in the train from the spindle to the
leadscrew, which may be fibre, and are meant to provide a "fuse" in the
event of a crash.

If you roll out a snake of plasticine and roll the gear over it, it
will leave a rack form impression. The number of degrees either side of
90, is equal to the PA of the gear.
Got a protractor?

The Super 7 bull gear is 60 teeth.. The most cost effective way to
change over is to rebuild the ML7, sell it, and buy a Super7. Decide if
you wish to rebuild the lathe, or build engines as a hobby.

The ML7 I had, had a 60 tooth worm grafted on to the spindle, to allow
the use of a dividing mechanism similar to a Radford dividing
attachment. I had the worm gear, but not the attachmentshrug. I have
some pictures around, somewhere, and will email them if you email a request.
To direct index, the cheapest method would be to mount a plate on the
back end of the spindle, with a index pin on an arm.

Cheers
Trevor Jones