wrote:

From a review of the literature including Milling Operations in the
Lather by Tubal Cain and Gears and Gear Cutting by I. Law (Work Shop
Practice series) [see http://www.powells.com for US source] and
Gingery's book Delux Accessories [see
http://www.lindsaybks.com/dgjp/djgbk/series/index.html ] it appears
that we can use a fly cutter and hand ground bits to cut the gear teeth
(spaces) to the proper involute profile, so no problem here.

However we do lack a way to index the gear blank.

Have you considered making Gingery's indexing head? That could be a neat
project for the class. Have you done foundry yet? If not, it can be
built up from plate and angle, plus assorted pieces of aluminum, brass,
and steel.

If the specified worm and worm wheel from Browning aren't affordable,
the thread tap idea another poster mentioned is a great idea.
I paid $40 USD for the Browning set but that was over 15 yrs ago, it's
sure to be higher. Still have it in a drawer, haven't made the index
head yet.

You might be able to salvage a worm drive unit, they are general stock
drive components with standard mountings used in industrial situations.
You don't necessarily need a 40 tooth wheel, but you may have to make
special index plates.

Speaking of which, one of Guy Lautard's Machinists' Bedside Readers
tells how to make master index plates using the like of toolmaker's
buttons screwed to a plate, against the edge of another round plate
whose diameter is accurately sized so all the buttons are touching each
other as well as the inside plate. When I used this technique my buttons
were turned from 5/16" nuts on an arbor, with the toolbit locked to
ensure uniform size. The backing plate was plywood, and the alignment
plate 12 gage aluminum plate. I had to shave a tiny hair off the
alignment plate several times to get all the buttons to finally touch
each other. I used hot glue to hold the buttons in place temporarily
during that trial and error session, then drove a drywall screw through
each button into the plywood.

I would highly recommend Lautard's books if you don't have them
already--they are a goldmine of info for what you are doing.

And my hat off to you and your associates for keeping alive what is
turning into a lost art of modern society!

Ken Grunke
http://www.token.crwoodturner.com/shop/


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