added an epsilon to the inside diameter of the rings to prevent bolts through holes resulting in 'WARNING: CSG normalisation resulted in empty tree'
switched to using cubes for hexagons
added 626 bearing size
Merge branch 'master' of github.com:benhowes/MCAD
use a numeric nema code for the motor number - could not get lookup to work though
Merge branch 'master' of https://github.com/benhowes/MCAD into benhowes-master

Conflicts:
	bearing.scad
	nuts_and_bolts.scad