An Ultimaker extruder big gear, for attachment on a non-threaded shaft.This is an accessory for the Ultimaker extruder update by ghagen01 rather than a derivative.It is needed if you have produced a 50materialwheel part without threading on its shaft - printed at shapeways in steel for instance, rather than machined.By the way I uploaded the 2 metal parts on shapeways :http://www.shapeways.com/model/530334/http://www.shapeways.com/model/530335/Update : V2 is beefier (previous version was prone to flexing) and has better designed nut holes (nuts were tending to rotate). Also from my experience, it's a good idea to have a bump drilled in the axe to allow one of the M3 bolts to avoid rotation.Update : V3 is stronger around the M3 nuts - the plastic here was prone to cracking when tightening too much in order to avoid the gear slipping on its axis.1) Print. 2) Shove 2 M3 nuts in the slots (pushing with a hot soldering iron may help). 3) Engage 2 short M3 bolts. 4) Push the gear down the 50materialwheel shaft, you might want to put a washer or two first. 5) Secure the 2 M3 bolts (easy on the torque, this is plastic). 6) Mount the extruder motor back in place, still wearing the stock little gear.As an alternative you could drill a M3 hole in the shaft and screw a single longer M3 bolt through the whole assembly.Don't forget to recalibrate your E_STEPS_PER_MM in the firmware as mentioned by ghagen01.Regarding the openscad model : This use the teardrop module from the MCAD library - https://github.com/elmom/MCAD. You don't need the MCAD files as a copy of the module is included in that file.The gear profile "large_gear.dxf" is an extract of the ultimaker lasercut sources by Martijn : http://www.thingiverse.com/thing:8563 You need it in the same directory this scad file is in.