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 extruder, its derivatives, and those used for 3D printers as Prusa I3, Prusa I3 Rework, etc.
The teeth are deep and sharp, which can guarantee a strong grip to the filament without applying excessive pressure.
1 x Hobbed Bolt M8x60 DIN 913 ISO 4014 8.8
1 x M8 autoblock nut (DIN-985 galvanized)
3 x M8 washers DIN-125A ISO 7089 galvanized