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Leather vs synthetic flat belts


Cast Iron
Sep 17, 2011
Use baler belt. The coefficient of friction between steel and rubber is higher than steel and leather. Less tension,therefore less load on the bearings. You might find a long serpentine belt too.


Jan 21, 2005
Rhode Island
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?

I have been very happy with the gear or timing belt turned teeth out that I put on my 10" Logan 25 years ago. Good traction if kept oil free and silent. No stretch.

Just a Sparky

Hot Rolled
May 2, 2020
Results are in:

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.
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Dec 21, 2012
Brisbane Qld Australia
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.


Aug 24, 2015
I have used a synthetic belt on my SB 10K for over 40 years. The first belt was slit off conveyor beting. There was no problem with grip on the pulleys. It failed after many years when the clipper lacing ripped out. I could not find anyone locally to install new clipper lacing so I bought a synthetic belt on line. It was slick and tended to slip. I could not find a source for belt dressing so I sprayed adhesive on the inside of the belt while it was running. It worked great.