Dumore 8574-210 hand grinder, series 9, 1/4 universal, 15,000 rpm the series 9 hand grinders are ideal for heavy duty grinding operations, including grinding weld seams, snagging castings, spark testing, porting and polishing engines. These hand grinders, powered by dumore motors high torque 1/4 hp fan cooled motor, idles at 15,500 rpm. Three heavy duty precision grease-lubricated ball bearings provide rigid spindle support. The threaded spindle allows for use of 1/4″ shank mounted wheels in a collet chuck or 3/8″ bore standard wheels.