I have a miniature Unimat 3 lathe & I put a file together some time ago about using the drive belt material & making the joins
.
The Unimat 3 & 4 lathes originally actually just used O Rings for drive belts but users found that high quality belts that last almost for ever can be made from the Polyurethane or Urethane drive belt material that you buy in cut lengths from suppliers.
For small applications the O Rings can work fine - they do on the baby lathes - so I gave some details about O Ring sizing but the drive belt material works better & last just about forever.
While my file was written specifically for the Unimat 3, I gave it a tidy & quick rewrite to make the information less Unimat focused. It is applicable for any custom belt job - especially for small pulleys & belts of the size likely to be used for drills for drilling PCBs.
Regards,
Brian.