The automatic polishing machine uses the discs from 8in diameter till they wear down to 6in diameter/ The machine polishes glass and metal. We usually take the used discs and put them on the pedestal grinder  or small handheld grinders and continue using them till they are 4in in diameter. However our polishing business has increased and we do not wearout  the used discs as fast as we create them, we are generating quite a stockpile of these discs that have much life left in them for polishing and deburring. The discs retail for 75.00 each