Ball Mills Mineral Processing Metallurgy13 02 2017· The apparent difference in capacities between grinding mills listed as being the same size is due to the fact that there is no uniform method of designating the size of a mill for example a 5′ x 5′ Ball Mill has a working diameter of 5′ inside the liners and has 20 per cent more capacity than all other ball mills designated as 5′ x 5′ where the shell is 5′ inside diameter and