It took another couple of tries, and the trick for these gears was to get the outer diameter to within 0.002″. Further, it required depthing the teeth to 1/32″ == 0.625″ (the precise measurement of the depth of the teeth) rather than cutting them a hair deeper. And I’m suspicious the Sherline divider may not be stepping the precise number of steps–but I have no way to prove that, and usually when I think equipment has gone south, it’s actually user error.
(Since, as I’ve said several times before, I have no idea what I’m doing here.)
And how did I get the blanks cut to the right diameter?
On the Sherline lathe, of course.
Because in the middle of the night last night I had a brainwave. I realized you don’t have to cut with the cutters straight on; you can turn the cutter so that it cuts off the carriage. Meaning if the cutting head is turned, the pointy bit that does the cutting is not over the carriage. Each wheel is only 1/8th to 1/16th of an inch thick, so it doesn’t take much. And of course be aware that you can crash the carriage into the wheel.
But that gives me about 3 inches and change of useful circle cutting power now–and that implies gears of up to 100 teeth at 32P. (For bigger wheels I’ll need to do something different–but my goal here is to design my own Orreries, and nothing I’ve designed so far require more than 80-something teeth.)
Anyway, good news, everyone!
Tonight will be some TLC with OpenSCAD, designing a new harness for the gears (so I can test to see how well they spin), and soon cutting the harness out of aluminum.