Hobbed Bolt for 3D printer, based on Reprap community design: http://reprap.org/wiki/Wade's_Geared_Extruder#The_Hobbed_Bolt
M8 x 60mm knurled at a standard meassure, 25mm from
the head of the bolt aproximately. This features are adapted to the
last versions of Greg's Wade extrud..
These precision pulleys are designed especially for the extrusion of the filament, its tiny teeth always guarantee a steady grip. 8mm inner diameter for use with planetary gear motor. Nominal measures: Inner diameter 8mm External diameter 12.64mm Effective diameter 10.8m..