I'm posting this for the brave at heart. I did one three plate using two sheets of plastic. Using square plastic I covered half the plastic with aluminum foil on one side and cut a plate from some sheet aluminum in a semicircle. stack the three pieces and drill a hole just above the foil. Solder the rotating plate to a rod that is the tuning shaft. Slide the other two pieces over the rod and put a dab of hot glue on the sides the hold everything together. You can use the blank disk that come in a box of cdrom.