Hobby Robot Gears
Choosing gear size and ratio for small robotics and mechanism projects.
Small robotics projects (rovers, robot arms, mechanism prototypes) usually want module 0.5–1 gears — small enough to fit compact drivetrains, coarse enough to 3D print reliably and survive the repeated loading of a geartrain.
Pick your ratio first, then your teeth counts: the ratio between two spur gears is simply teethdriven / teethdriver, and the catalog's 10–60 tooth range covers ratios from roughly 1:1 up to 1:6 in a single stage. For bigger reductions, stack two stages (e.g. two 1:3 pairs for 1:9 overall) rather than using a single very-uneven pair, which wears faster and is noisier.
Match bore diameter to your motor shaft or bearing — the default bore on every downloadable gear is sized from its module and pitch diameter, but the generator lets you set an exact bore if you need a press fit onto a specific shaft.