I'm going to replace the AC motor on my Lathemaster 8x14 lathe with a
DC treadmill motor as I want varible speed. (I checked & can't find a
3-phase motor that small, otherwise I'd use a VFD).

Anyway, the original 1 HP motor has a 16mm keyway shaft (0.630") and
the new DC motor has a 5/8" (0.625") keyway shaft.

How do I deal with the 0.005" difference? Is 0.005" within the normal
tolerance range for pulley ID's and I can forget it? Or should I
machine, split, and press fit a very thin bushing into the original
pulley set? I want to use the original pulley set as it includes a
timing gear.

Regards,
Ed Ferguson