For a diametrical pitch of 16, the recommended backlash (American Gear Manufacturers Association) for each spur gear is 0.004" +-0.001". This would generate in a backlash of 0.016" for the entire train (5th gear not shown). Since the backlash between any two spur gears in the apron must be a few 0.0001". Rivett wouldn't have it any other way. In addition, there are more ball bearings in the apron than most lathes have in entirety (30 ball bearings).