We specified a runout tolerance of .0002″ to .0005″ (that’s 2-5 ten-thousandths) and our machinist has finally cleared his bench to develop a quality control process.
The pulley is a small part, but it would be a mistake to underestimate it’s contribution to the precision of the drive system, and it’s deserving of a rigorous quality control procedure.
Holding these tolerances results in a degree of speed stability that’s well below the threshold of perceived pitch stability (wow & flutter).
In this domain, speed precision is perceived as lower distortion and for lack of better terminology, more musical engagement.
Shown here is a pulley chucked up to the lathe.
(click images for a larger view)