i decided to do a little test as i wasnt sure how urethane wheels would react on the lathe. turned out its like butter, you just need to crank up the speed as fast as possible otherwise the cut isnt clean. once i knew it would work, i ordered 10 sets of wheels from a wholesale place.
i decided to use 6mm thick tempered glass. call the glass shop and ask what size holes they can make before you start... i got lucky... i machined the wheels at 38mm, and they could do 40mm holes in the glass. the 2 mm difference made everything fit much better!
i made a tool to hold the wheel in the lathe from its center, then the first step was to make one side flat. that side will be the back. i did all 38 wheels, then moved on to the next step. i grooved the front part of the wheel where the washer will sit. i then cut the wheel removing the entire front part, and then machined it so that the center diameter is 38mm and 6mm wide.
it took me about 8 hours to make all 38 wheels, and at least 1 to clean the entire shop... urethane dust is sorta sticky... oh yeah, wear a mask when you machine it!