### Basic Ball Mill Grinding Circuit

The speed of mills depends upon their diameter; a ball-mill of 3 feet revolves 35 times a minute, and one of 5 or 6 feet, 29 or 27 times. Tube-mills run at a revolution or two faster (see Fig. 117). Some ores require much finer grinding than others to liberate the minerals, and this increases the milling cost. Ball Mill Product Classifying