Draw Gears in Rhino 3D

This is a RhinoScript that creates involute gear tooth-profiles (including bevel gears) around any circle in any viewport and any orientation. It will treat the circle you pick a the 'pitch circle' and it will draw the gear teeth around it. You can specify the gear either by number of teeth, or by its module.
GearGen - Involute Gear Generator Download

This is just one of many scripts on Thomas Anagnostou's Rhino 3D Script website.