I can’t really imagine making wood gears for anything other than some of the woodworking machines like those made by Matthias Wandel, to make some of those cool wooden clocks you see on the Internet, or just out of curiosity to see how some DIY plywood gears work. And that’s where I’m at, testing how well they work if I cut them with my DIY table jigsaw.
In order to make your own gears that work and engage well one with the other we need to start with a good design, and probably the easiest way to design them is to use the Woodgears gears template generator. It is easy to use and helps to make lots of different plywood gears. If we are going to do a specific project we will need to design the right gears, but if as in my case we just want to practice cutting them to see how they look and work, we just need to make sure that both have the same size teeth.
Cutting gears by hand with the jigsaw I don’t think is possible, but making them with the help of the homemade jigsaw table, with its guide with bearings to keep the blade vertical, it should be a simple task. At least I managed to make pretty decent wooden gears on my first attempt. The biggest problem I found was when cutting the top of the teeth, but by drawing a straight line on each tooth helped me get closer during the cut, and so I was able to cut the top of all the teeth without the fear that the cut would end up tilted. When making these cuts I thought that a jig for cutting circles with this jigsaw table might come in handy, although I don’t know how well the teeth would engage if I approach the top of the teeth with a circumferential curve. Anyway, now I can see that cutting perfect wood gears of plywood is going to be a complicated task. I’ll just have to settle for good gearing between them.
Cutting the shape of the teeth is easier, as long as we do not insist on cutting the curved shape of the tooth all at once. The curve that shapes the tooth gets tighter as it approaches the base of the tooth, so there comes a point where my saw is not able to follow the curvature and I have to leave those areas uncut (like the uncut corner inside the red circle in the picture). But it is easy to finish those cuts once most of the material between the teeth is removed.
To finish making gears with this method I have to cut the area between the teeth. To do this I made cuts perpendicular to the line that marks the base of the space between teeth, and then I slide the gear to the sides to rub the jigsaw blade against the line [5]. And surprisingly, the result was quite clean. In any case, it is advisable to use a straight file to go over the bottom between the teeth and the shape of the teeth so that they engage more smoothly.
After cutting plywood gears we will always want to see if they engage and work. To test the operation of these plywood gears I mounted both with screws on a piece of plywood board. I used those smooth shank screws that have a smooth area between the head and the thread, so they will work well as pivot axis. And a simple nail served as a lever to turn them. On the first attempt they jammed a little, but by checking which teeth were jamming and touching them up a little with the file, I managed to get them to engage well without any problems.
And see also how to make plywood gears, but with smaller teeth. I think they are easier to cut:
