Watch Lathe Drive Belts
For 30 years or so, the only drive belts I have used on my watch lathes are 3/16" hollow Rounthane. That is a polyurethane material that is hollow, like hose, and comes in either yellow or clear color. You cut it a bit short and join it by pushing the ends over a tiny barbed aluminum connector. The belt comes in 100 foot rolls and the connectors come in bags of 25. The belt dealers make me buy 200 feet at a time, so I got in the habit of selling my excess belt and connectors to other watch and clock lathe users.
The same material is available solid instead of hollow. The solid belting must be welded, which is possible, but I never wanted to bother. I do have the actual expensive electric welding tool made for these belts. Welding can also be done with a heated knife blade. Welding leaves a flash around the weld that is a pain to trim off.
Rounthane is available in a variety of sizes and materials, hollow and solid. They also make a v-shape belting that can be welded to any length.
Obviously this stuff is great for applications like a watch lathe where it is a royal pain to pull the spindle and install an endless belt.
http://www.shinglebelting.com/extrusion.html#rounthane
Many years ago, leather was the normal round belt material for little machines. Levin actually made a splicing tool for gluing leather belts for their lathes. O-rings do not work well at all for high speed belting. Steel spring belts slip like mad if you try to use them on a lathe. Some machines use endless round belts made of braided cotton or synthetic thread. Examples are the Alexander (Deckel copy) cutter grinder and the old belt-drive dental engines. These belts are good, but hard to install on a watch lathe, even if you could find one the right size.
The Levin bench I use has the motor below the benchtop, driving a countershaft behind the lathe. The motor belt is a 2L section v-belt. The countershaft comes apart easily, so the endless v-belt is not a problem.
For a 10 mm lathe, I use a 1/8 or 1/4 HP universal motor of 5000 to 10000 RPM. I control the speed with a Linemaster solid state (SCR) foot control. Mine is a cast iron Clipper wide tread type, which I did not find on their website. Here is one that will do the same job:
http://www.linemaster.com/acvarspctl.shtml
The Foredom model SCT-1 foot speed control is about the same as the Linemaster Clipper and may be easier to find. See P.7 of the Foredom catalog.
http://www.blackstoneind.com/foundations/store/documentwarehouse/documents/301Catalog_AllPages_May2006.PDF
Larry
[ 08-24-2007, 08:42 PM: Message edited by: L Vanice ]