GRINDING Urethanes 55A to 80A durometer can be ground successfully in an engine lathe using a tool post grinder. Use low turning speeds -- below 150 rpm, with the lathe running in reverse. Start with the grinder feed rate set .005 inches per revolution. Use a slower feed to improve surface finish or to remove more material by taking a deeper grind. We have found that a Radiac Por-Os-Way 46 grit wheel with slight radius on the leading edge works well. RPM of the wheel should be in the 2250 to 3250 range. Again, low work piece turning speed of 150 rpm is a good starting point. Fine abrasives can be used for final polishing. Urethanes above 80A durometer usually require some type of coolant, however, they can sometimes be ground dry. Water is a good coolant, and can be applied with a brush or with a fine spray mist. We recommend that the grinder be equipped with a dust collector or the operator wear an approved dust mask when grinding or sanding urethanes. NEXT: Drilling