It works on the principle of impact and attrition size reduction is done by impact as the balls drop from near the top of the shell A ball mill consists of a hollow cylindrical shell rotating about its axis The axis of the shell may be either horizontal or at a small angle to the horizontal It is partially filled with balls The grinding It works on the principle of impact and attrition size reduction is done by impact as the balls drop from near the top of the shell A ball mill consists of a hollow cylindrical shell rotating about its axis The axis of the shell may be either horizontal or at a small angle to the horizontal It is partially filled with balls The grinding