Spur gear pair

Two gears that actually mesh: pick the tooth size, the tooth count of each gear and the pressure angle, and both are generated with proper involute teeth and placed at the exact centre distance, turned so the teeth interleave. Bores, hubs and face width are yours to set, and the backlash slider is the number to tune so printed teeth run freely. The readouts give you the pitch diameters, centre distance and ratio to build the rest of your mechanism around.