If you ever decide to design something mechanical, eventually you’ll need some gears. I’ve been experimenting with laser-cutting gears.
The first thing I found out is that drawing gears is hard, they are complex in ways you might not realize at first. Gear teeth aren’t simple squares, or triangles, or a easy combination of the two. The teeth are angled based on the diameter of the gear and the pressure angle. See the two following images to compare a small diameter gear and a large diameter gear with the same size teeth (20px) and pressure angle (20).
Luckily there is a easy tool for creating gears, the “Gear” effect in Inkscape. This is how I make my gears for laser cutting.
Inkscape is an open-source vector based drawing program, similar in some ways to Adobe Illustrator.
To create a gear in Inkscape simply go to Effects > Render > Gear. A dialogue will appear that lets you choose how many teeth, and how big you want the teeth to be for your gear.
Once you have you gears created you can export them to your laser, cnc, or other drawing program. Inkscape has many vector based export formats including DXF, SVG, and EPS.
Here are two good pictures from some test gears I’ve cut, the large wooden gear has teeth that are about 4mm each, the acrylic gear on the ruler is the same model at 50% size (2mm teeth).
I'm pleased with the results of the laser cut gears. Acrylic tends to melt into rounded edges with thicker material, the thinner it is the better the teeth turn out.
Update: I've also found a flash-based gear generator, it's somewhat cumbersome, but it does not require you to install anything, you can find it at: http://woodgears.ca/gear_cutting/template.html.
Update 2: I've also posted another project (Laser cut gears 2) with gears that has teeth that are 0.5mm across, about four times smaller then the small teeth on this page.