For determination of resistance to wear by attrition. Two iron cylinders 77/8" dia 133/8" long with dust and water-tight covers, mounted on a shaft with their axis inclined at 30 deg. to the axis of rotation of the shaft. Rotation speed is 30-33 r.p.m. Driven by 1 h.p. three phase 440 volts, A.C. Electric motor.