Making wooden gears out of plywoodHere's some pictures of making wooden gears out of plywood using paper template from my Gear Template Generator.
I made two gears, both with a tooth size of 250, and tooth angle of 25 degrees. The smaller one with 7 teeth, the larger one with 11. With that tooth size, 11 teeth was as large as I could go before I would have had to paste multiple pieces of paper together.
Normally, one doesn't make involute spur gears with less than about 14 teeth. But I wanted to test the limits in terms of how few teeth I could get a away with and still have the gears turn smoothly. Experimenting with the template generator and watching it animate, I decided that 7 teeth would barely work.
I printed out the template on an ink jet printer, and glued it on a piece of plywood with a few dabs of glue.
I drilled out the corners of the gear first, and put a 1/8" wide 'scroll saw' blade in my bandsaw.
A scroll saw would perhaps be even better for this job, but I didn't have one at the time.
The next step was to trim the teeth a little bit. I used a large file to remove any small bits where I cut outside the line and to smooth the curve of the teeth.
I suppose a strip sander like this one would have come in handy for this job:
I put two dowels into a piece of oak, and added another dowel to the larger of the two gears as a crank.
The two gears run amazingly smoothly, especially considering the small number of teeth in the gears.
Somehow, it's just compelling to pick up the gears and start cranking them and see how fast they will go.
What helps these gears work so well is that I made them from some very nice plywood - Russian birch plywood, which has very fine plys all made of birch. I'm pretty sure this wouldn't work nearly as well with ordinary coarse spruce plywood.
I generated the shapes for these gears with my free online gear template generator. However, I have since written a more powerful gear template generator program, which you can buy online.