Step 2: Tests, plans and machining.
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!