So I drew and cut out several blanks from the 1/8th inch aluminum (and I confess I had to do this several times, by the last blank I was very close to the line) using a scroll saw and a jeweler’s blade.
I then perfected them on the Sherline Lathe to the correct diameter of (29+2)/32 inches, and drilled a 2.5mm hole in the middle.
I made two mistakes; the first was that I got the depth of the teeth wrong; I figured the depth of the teeth would be 4/32 inches–which is the difference between the outer diameter and the inner diameter, not the difference in the radius. (So the teeth should be 2/32 inches deep not 4/32 inches deep.)
Go back, make another blank.
Second mistake: the three jawed chuck (shown in the photos) can’t really hold the load during cutting. The gear and arbor got loose, screwing up the gear. Replace with 4 jawed chuck. Re-cut mounting arbor (since old one was trashed).
Go back, make another blank.
But finally, I got my 29 tooth gear. And it even meshes properly with a commercially purchased 32p gear I bought from SparkFun:
Only 6 hours of my life, too!
(But now I know the process I think I can shorten the time somewhat…)
One down, 6 to go for my Earth/Moon orrery.
The Hacking Den 