From owwm.com forum thread http://www.owwm.org/viewtopic.php?t=22194 by Eric LaVelle
After some months of studying, acquiring tools and supplies, and working, I've completed making leather belts and tested them on one of my machines.
I started with 6 sides of heavy harness leather, a linoleum knife, a 4'X8' sheet of OSB board, a straight edge that is actually the back splash of a science lab counter top. The first step was to cut the hide into "butt" and "shoulder" sections.
The butt section was then squared and cut into strips running the length of the hide. The best belts come from the center of the back of the animal "center-stock". The shoulder area can be cut into strips cross ways. Then neck area is too weak and spongy to use as belting. The belly of the hide is also not good belting material.
The butt stock strips are about 4 1/2'-5' long.
For single thickness belting, the strips are turned so that the front end of one meets the front end of the next such that they are put together each alternating the way it was on the animal. The reason for this is that the areas further from the center of the back of the animal stretch more, causing the entire belt to curve if the strips are all run the same way.
In order to join them, I first used a paper cutter to square the ends, then marked them to cut tapers on the ends to lap and glue them.
In order to cut the tapers (6" tapers for belts over 5" width, 5" tapers for 3-5" width, and 4" taper for widths under 3"), I bought a tool called a leather splitter. This one is an Osborne #84.
The splitter tapers the thickness. It's manual, so it takes a bit of practice, but it's much faster and more accurate than trying to use a hand plane or a sander. As you pull back on the handle of the splitter, the roll under the blade raises, bring the leather further up into the blade.
I laid out the skived pieces against a straight edge and coated the joints with barge cement:
I let them dry for about 10 minutes, then put them together, put a piece of 1/4" craft foam on top of them, and hammered them together. I weighted the laps down while hammering so they wouldn't move around. A press can also be used instead of a hammer. The books say not to hammer the joint directly. I'm not sure why, perhaps it will damage the leather. I let the joint dry for at least a half hour before I went on to the next one. I coiled the belts as I went along:
The total belt length should be the length measured around the pulleys minus 1/8" per foot to give proper tension. The belts will stretch and will have to be taken up a couple times. I found the stretch on my lathe belt to be rather annoying. I plan to pre-stretch them from now on using a scale with a weight hung on it, draping the belt over a pulley, and clamping the other end in a vise. According to the book "Pulley & Belt Transmission", the tension for stretching should be 90-120lbs per inch of width, and it should be stretched for a couple days. Another way to deal with stretch is to use clipper lacers, cut the belt 6" short, and add a 6" removable piece which can be changed to 4", then 2" then taken out altogether.
The proper belt dressing for leather is neatsfoot oil. The belt surface should feel like the skin of your hand when it's warm.
Estimated useful life of a leather belt is upwards of 40 years if it is rubbed with neatsfoot oil a couple times a year.
This process may only be worth the effort if you need belting for more than one machine. I needed a total of 304 linear feet of belt ranging from 4 1/4" down to 1" width. My total cost was $815, and I have some leather left over. Mcmaster-Carr's price would have been $3973.20, giving me a savings of $3158.20.
I got the leather from http://www.kyleatherandhide.com/
for $100 per side plus shipping. I also got my barge cement from them. One quart was enough for all the belting I made with some left over.
I took my time making the belts and learning as I went, but I feel a dedicated person could finish the task in 2 or 3 weeks. The slowest part is waiting for glue to dry.