Wheel and Pinion Cutter
To make a clock one must have a way of forming the "teeth" on  
the gears (wheels and pinions) that transfer power from the
motive force appropriately and as efficiently as possible>>>>>

An excellent book on the subject is F. Malcolm Wild's
Wheel
and Pinion Cutting in Horology
. Like most horological books,
you will not find it at your local Barnes and Nobles, but it is
plentiful online.

To cut the teeth to make gears one needs:

1)
A method of firmly holding the blank to be cut
2) A method of indexing the blank (ie. if the wheel will have 40
teeth you will need to be able to turn the blank 1/40th of it's
circumference after each cut.
3) A cutter and a method of holding the cutter
4) A method of turning the cutter at a high enough speed and
torque to be able to smoothly cut the blank.
5) Ability to adjust the X,Y and Z axis.

Things that are nice to have:

1)
Ability to vary the speed of the cutter  
2) A safe set-up that does not involve any part of your body or
clothes within the machine's realm. This actually should be
mandatory....
3) Commercial multi-tooth pinion cutters, as single-toothed
flycutters will not hold up to steel.
4) A completely single purpose wheelcutting station, so you
don't have to tie up your lathe or milling machine.
5) A Lever Feed, or better yet, a CNC set-up.
6) A built-in coffee maker. Though I have yet to see one......
7) Lots of money. To, instead, buy a really nice one with an
assortment of cutters.
I've cut gears on my milling machine before and it's a very
suitable arrangement. But I hate either tying up a machine that
gets used alot, or, having to knock down and set up a whole
wheelcutting system just to cut a 1-off wheel on a machine that
gets a lot of use in my shop, so I decided to make a separate,
single-purpose station to cut gears (see
Things That Are Nice
To Have #4
above).

Items #1 and #2 (and most of #5) on the
Needs list above are
easily satisfied by the "semi"-universal dividing head >>>>>>
that I have in the shop which is bolted to an XY milling table.
The threaded spindle end accepts a standard thread (1 1/2"-
8) 4-jaw chuck which grips a threaded arbor holding the blank.
The 4-jaw can be fiddled with (in conjunction with a dial
indicator) to reduce the run-out down to almost nothing.
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Homemade flycutter forming the teeth (very badly, I might add)
on a contrate wheel.
My 'semi-universal' dividing head....proud and
unconcerned that it is not a 'universal' dividing
head...
A note on "semi"-universal dividing heads, particularly for
clockmakers. They can divide a wheel into most
any number
that a clockmaker would ever run into (there are some funky
numbers that you would need a "universal" head which
employs a separate set of gears to get you there). I was
surprised, however, to find out that, even with the wide
variety of index plates supplied with the head, I couldn't
divide a wheel into 96........
96?!! You'd think it a common
number!! Well, after much head scratching and a couple
glasses of wine my head cleared and I figured out if I had an
index plate of only 12 (which most don't) the 40:1 worm ratio
would give me the 96 I needed. So I chucked up an index
plate on its own dividing head (it seems rather cannibalistic)
using a 3-jaw chuck (jaws turned out) and drill a 12-hole ring
around an unused portion of the index plate. And It works!!!!!!
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