Bead chain gear for stepper motors with 5mm shaft, e.g. for Polargraph plotter

A remix of the bead gear found here http://www.thingiverse.com/thing:42188 - I only added a part ready to be put on a 5mm shaft of a standard stepper motor. The shaft can be fixed with a M3 screw from the side.
On my printer the 5mm hole was a bit too tight, a bit of work with a 5mm drill fixed this. The M3 makes its own thread when screwed in.