Hi Jim,

This is one of several standard ways to make gear cutters for clock and
watch work. You can make an offset mandrel to allow the turning, then
remove a section of the disc. Another option is to drill a smaller hole
to secure the cutter for turning, then enlarge the hole with some offset
to provide clearance. When mounted on a standard arbor there is
sufficient clearance all around. For brass there is no rake, so you can
restone the cutting surface quite a few times before the cutter is too
far gone to use.

At least one guy slices four cutters from each disk, and mounts then in
a slot on the face of his cutter holder. Quite a few ways to skin this
cat when simply turning the profile on a bit of drill rod and then
grinding a D style cutter isn't quite good enough.

Here's a link with a photo of a commercially made gear cutter in this style:

http://www.clock-keys.com/pdf/116.PDF

And some sharper pictures of similar ones at:

http://www.timekeepersworkbench.com/cutters/

A slightly fancier version (four cutting teeth) is described at:

http://www.metalwebnews.com/howto/gear/gear1.html

Seems there's a few sets of online instructions floating around for
making single and multiple tooth cutters, but I'll be darned if I can
find the all of the links right now, maybe a DNS down somewhere. John
Shadle has some really good instructions on combining the flycutter
style with the turned form disk approach. The link to the articles
(which are in Word format) is:

http://onlineclockbuilding.com/download.html

If you are interested in clocks, check out the rest of John's site, he
does some very neat stuff.

Neat little gadgets, not sure I'd try to cut a 4DP with one, but very
effective in clock and watch sizes anyhow. You do have to do a bit more
to generate the correct shape for low tooth count gears, such as
pinions, but for the usual 30+ tooth count clock wheels these work
nicely. In clock work you are gearing up be large amounts, rather than
gearing down as we usually do in machine tools. The tooth form is
usually cycloidal or a variation as lower friction is more important
than power transfer in clocks and watches.

Cheers,
Stan

jim rozen wrote:

In article ,
says...


Don't mess about trying to grind HSS for the bits - it's so much
easier to turn carbon steel drill rod to the right profile in its soft
state in the lathe and then flame harden it.


Hmm. So you initially use a lathe to turn a *round*
part, with the correct taper shape to just fit inside
the space between the gear teeth, and then remove
about half of it to make the fly cutter?

Jim

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