Customizable coupling with a keyed shaft for fitting an M8 motor shaft into trolley wheel

This thing is a coupling for hooking up an M8 motor shaft to a trolley wheel that has a keyed internal shaft. It's then secured in place with a printed M12 nut.
This thing is maintained at https://github.com/hyperair/motor-wheel-coupling, and depends on https://github.com/hyperair/MCAD.

Updates:
2014/08/17:
Make the motor shaft hole render with a flat portion rather than fully cylindrical. This helps spread some of the load across the entire shaft rather than being fully reliant on the