ReDo has one gear, the Spur Gear, in seven sizes: 8, 12, 16, 20, 24, 28 and 32 teeth. They all share one tooth size, a module of 1.25 mm, so any two of them mesh.

An 8, a 24 and an 8 tooth gear on a plate: each pair is 20 mm apart, two grid cells, so all three sit on holes.
An 8, a 24 and an 8 tooth gear on a plate: each pair is 20 mm apart, two grid cells, so all three sit on holes.

Gears that meet on the grid

A gear's working size is 1.25 mm for every tooth: a 16 tooth gear is 20 mm across. Two gears mesh when their centres are half their two sizes apart, and that distance lands on the grid when their tooth counts add up to a multiple of 16:

TeethCentres apart
8 and 810 mm
8 and 24, 12 and 20, 16 and 1620 mm
16 and 32, 20 and 28, 24 and 2430 mm
32 and 3240 mm

Put each gear on a grid hole and pick a pair from this table: they mesh.

Bevel gears

For a drive at right angles, tick Bevel on a Spur Gear and choose the gear it meets. It builds the same teeth on a cone, so the two mesh at 90°.

In the Playground

Gears that mesh can be coupled, so turning one turns the other: select one and choose Couple under Gears in Tool Properties. See Assembly Mode.