For the past 5 years, the only part of the rock tumbling setup that feels uncontrollably delicate is the belt. The tumbler has a steel frame with rollerblade ball bearings for every motion point, but the belt still remains a weak point. Short of a direct drive, I've tried every brand of rock tumbling belt (for this class of tumbler), plumbing o-rings, rubber bands, hair ties, auto radiator cap gaskets... seemed like heat and months of strain through the small pulleys took its toll. Wish the system was as robust as a vacuum cleaner drive system..... AAAAAHHH HAAAAA!
Out with the round and v-shaped belts and in with the nylon-reinforced flat rubber vacuum cleaner belts! Oh, crap - outfitting the Fasco motor and the tumbler's 1/4" shafts with pulleys that match the shape and diameters that I need will be impossible. I could reconfigure the drive distances to retrofit stock pulleys from McMaster Carr or Grainger ($30 a piece!) but that would require rewelding the frame a little. Pass.
I thought if I had a lath, I think I could make exactly the pulleys I needed to run with stock vacuum cleaner belts... then I remembered I hadn't run a lath since 1981. Let's start the in-shop improvisation. Start cutting, and the hope solutions follow. I knew scroll sawing perfect circles was out, decided to try a set of drill-mounted hole saws.
Cutting perfect disks
I needed decent plywood (hardwood with a high ply count) and a hole saw set that had larger dies, 3" or larger. Know that a tight pulley diameter contributed with belt wear - I wanted pulleys of 3" for the smallest one, then calculate out the needed diameter to maintain the correct rpm that I had been using.
As with a lot of Harbor Freight items - the tools usually work as advertised but wouldn't last in the hands of a general contractor. The Harbor Freight hole saw set does the trick for this.
Good good. Now what? Same as 30mins ago, I still don't have a lathe. I'll "chuck" this ro ugh cut disk ontop a 1/2 20 screw and ... do something with it on a drill, best guess would be to drag a square file across it to create the flat channel. Doh! No small flat file! Shift to trying a zaw saw blade, glovelessly hand-held of course.