this grindability test is conducted in a. bond ball mill of d / l 0.3048/0.3048 m dimensions at the speed of 70 rpm. the. mill is loaded with 21.125 kg standard sized balls and 700 cm 3 of,kinetic grinding test approach to estimate the ball mill,kinetic grinding test approach to estimate the ball mill work index 347 table 4. obtained p 80 n r equations for all samples sample no. ore type p 80 2 n r r 1 bauxite p 80 3 (2e06) n r 0.0014 n r 2 0.3094 n r 87.923 0.968 2 hematite p 80 3 (1e06) n r 0.0011 n r 2 0.2803 n r 83.408 0.9971 3 3chromite1 p 80 (2e06) n r 0.0017 n r