The range of the smooth-face rolls, for example, is from about 400 ft/min for the small 12-in. rolls, to 2000-2200 feet/minute for the heavy-duty 72″ machine. The single-roll crusher has a tip speed of 400-450 ft/min while the 6- x 7-ft teethed roll crusher has a normal, no-load, surfaces speed of just under 3500 ft/min.