maximum safe operating speed marked on wheel. 3. DO USE MOUNTING BLOTTERS when supplied with wheels. 4. DO BE SURE WHEEL HOLE, THREADED OR UNTHREADED, FITS MACHINE ARBOR PROPERLY and that flanges are clean, flat and of the proper type for the wheel you are mounting. 5. DO ALWAYS RUN WHEEL IN A PROTECTED AREA at least one minute before grinding. 6.