Looking to order a new flat belt for my 13" South Bend. The one I've got in it now is a bit long and I've run out of adjustment to take up the slack.
Before I re-order from the same supplier as before, I'd like to learn a little more about the different material options available out there. Right now I'm running a three layered composite Nycor belt. The fact that it doesn't stretch and I will never have to chase it is nice, but it's hard, textured surface is not very grippy on a smooth, polished flat belt pulley. I find that it takes considerable tension to prevent the belt from slipping when taking a reasonable 50+ thou cut in 6061. Yes, it's only a 1 horsepower machine, but I know the motor's got a little more grunt in it than that. Big heavy Century machine tool motor with a 1.25 service factor.
Are leather belts any tackier than the synthetics? Are there grippier options out there to choose from?
Oiled leather adjusted as tight as I can possibly get it while still leaving barely enough slack when the tensioner is released to change pulleys: Slips when chuck is locked in place and exposed to motor starting torque. Motor will successfully start and reach full speed in this condition. Also slips when load is applied well before motor breakdown torque is reached. Talking a 70 year old 1 horsepower single phase motor with paper start capacitor here. Nowhere near the modern 2-3 horsepower three phase units sometimes seen in these lathes in terms of torque figures.
Rubber belt adjusted moderately tight: Holds fast when chuck is locked in place and exposed to motor starting torque. Motor maintains locked rotor state in this condition. Does not slip when applying as much drag on the chuck as I possibly can by hand. (Do as I say, not as I do, yada yada.)
Rubber belt wins hands-down in a 13" South Bend. No contest.
For the budget minded ,Ive found car multigroove belt to be a free source of effective belting for old machines.......run grooves down ,it grips smooth pulleys well ......I have tried skiving and glueing,but eventually the glue cracks......so ,the most effective method Ive used is lacing with weed snipper cord ,Stihl cord being indestructible in this application.........I have a small bank of belt machines that can be displayed at engine rallys as a load for an engine..........As an example the belt salvaged from a V6 Buick (about 1&1/4" wide) happily runs an old drill punching 3/4 holes in steel plate without slipping.............incidentally ,the V6 Buick/Holden belt is the longest of the car belts.