Abstract: A closed system, impact-fatigue test machine for grinding balls comprised of a vertically extending guide member and a lift conveyor wherein the guide member lies above a recessed anvil and defines in its center a longitudinal opening. Each grinding ball is carried upwardly by the conveyor to an opening in the upper portion of the guide member and then is dropped into the guide member to land laterally supported, upon an earlier dropped grinding ball which rests on the anvil below. The earlier dropped ball is then pushed from the anvil toward the conveyor causing the dropped ball to impact the anvil below. The number of dropping cycles that each ball can tolerate without fracture is counted by a counter. Fracture of the balls is detected by a fracture detector.