Behold and fear my Skulltruder!
This is a set of spur gears for Wade's extruder.
Derived from Cleaned Skull by ssd
( http://www.thingiverse.com/thing:4126 ). I use these on all my 3D Printers.
Notice that there is a cap for the bolt the skull on the larger gear - may need a wee bit of sanding around the perimeter for a proper fit. This should seat at the proper depth for stealthy concealment of your secret hardware. Upgrade your Printrbot with these gears from Shapeways in Laser-sintered nylon for greater precision and consistancy.
I ditched the small skull on the small gear. It never printed well with the hole through the forehead and the reduction in size. The NEW! small gear has some nice features, including cleaned up teeth, and a flat bearing surface for the set screw.
See the picture with the black and the white gears:
The Black gear came with my Printrbot Plus kit. The STL file shows a diameter of 63.78 mm. The gear that was printed by a Printrbot in my kit measures 61.25 (averaged 8 measurements) The white gear was printed by Shapeways in Laser-sintered nylon and averages 63.25 mm