I posted asking about flat belts. Being a cheapskate I managed to move the upper shaft and repair the old belt. I have for years run the belt over pulley that have cloth glued to them, it stopped the slipping. After repairing the belt I changed the speed, first time in twenty years;-) and I am now running it on clean metal pulleys.
The belt slipped like hell on the nice shiny metal pulley's. I was taking a 20 thou cut while boring a 12" hole in an ali casting and it was slipping so I poured some sodastream cola concentrate on the pulley and it happily took a 150 thou cut with no slipping!!!
It's quite intereting to to watch and hear when it's taking a heavy cut. The belt sticks to the pulley making a tearing noise as it's pulled off the pulley and the belt is stuck to the upper pulley for a greater angle the deeper the cut, pulling the belt tighter.
The pulley has a residue that looks like contact adhesive on it now. It needs about a teaspoonfull of the stuuuf per casting i bore and face. The improvement in surface finish now I am not doing the maching in backgear is great and it's muuuch quicker so I am a very happy bunny..
So things do go better with coke.