One day I intend to make a watch.
I’m still a long way off, but tonight I made a good step in the right direction :)

A large part of a timepiece is of course the wheels and pinions. I’ve been contemplating how to cut them without bankrupting myself buying the cutters.

The Sunderland gear planer uses a fairly simple cutter for racks, and generates the curves of the spur gears by coordinating the cutting and a rotation, so the gear blank rolls against the rack as though it already had th teeth.

I have several old engineering texts with some of the relevant details in:



Of course I don’t have a gear planer, and generally they are for much larger gears, but I can use the technique with a little bit of lateral thinking.

First make a rack form cutter, simple lathe work.



Then wack it into an indexer on the mill



And create some flutes for the cutting edges.



Then handily I have recently bought a kiln (for enamel) which I can use to Heat treat. So much easier than a blowtorch.



I decided to keep the tooth count smallish for my first gear - 30 teeth /12degrees each. That also means I can use the simple divider. To assist my little brain I wrote down all the teeth angles so I could tick them off as I go.



Then it’s a question of put on the right cut and index /cut / repeat...



Once the first pass is done I rotated the indexer by 6 degrees, moved the cutter by an equivalent linear amount and cut it again. This generates the tooth curves.

The end result is gear shaped:



And meshes with another 48dp gear nicely.



I got a beautiful pattern when parting the gear blank off the stub it was machined as part of.



There is more work to do, but I think the method will work without too much effort.

Dave