The Critical Speed for a grinding mill is defined as the rotational speed where centrifugal forces equal gravitational forces at the mill shells inside surface. More details Get Price Calculations for mill motor power, mill speed and media charge May 17, 2021 Rod mills, how they function The Critical Speed is used for the determination of ball mill ideal operating speed But for comparison, rod mills would operate between 50% to 95% of the critical speed The faster the mill speed, the greater the wear on the rods and liners So, the general rule of. Critical speed (CS) is the speed at which the grinding media will centrifuge against the wall of the cylinder. Obviously no milling will occur when the media is pinned against the cylinder so operating speed will be some percentage of the CS. The formula for critical speed is CS 1/2 (g/(R-r) where g is the gravitational constant, R is ...