Extruder Knob - 5mm shaft

I needed a better knob than the stock for the EZ-Struder on my Rostock Max V2, by SeeMeCNC. Original slipped on the shaft, and hurt my hands to turn since I don't have calluses, ha. So, I whipped up this new one. Fits tightly on the shaft.

This should fit any 5mm diameter shaft, with a 0.5mm cutout for the setscrew.

Edit 20161206: updated scad source with better parameterization and depth of shaft cutout, and added two improved models. Both new files (20161206) for 6mm shafts -- on