It was an A section Powertwist belt..
It could drill 20mm holes in mild steel from14mm.
Going from 12 to 20 was a marginal affair.
Belt tension was not high as I liked the slipping when I made something stupid.
I have stalled a 4 pole 0.75kW motor once.The white video one.
Powertwist A belts cannot go round smaller than 60mm pulleys.
Do You have a drawing of the drive system?
My Boxford back-gear system was only used for unscrewing chucks,faceplate etc.
When starting with both backgear and direct drive engaged, belt slip was a benefit.
Edited By Niels Abildgaard on 18/02/2019 06:40:30