Mill Critical Speed Determination. The "Critical Speed" for a grinding mill is defined as the rotational speed where centrifugal forces equal gravitational forces at the mill shell's inside surface. This is the rotational speed where balls will not fall away from the mill's shell.

A Ball Mill Critical Speed ... Within that range the power is nearly proportional to the speed. Mill rotating speed impacts grinding rates. ... This video should the working principle of a ball mill and the ball action at various speed near up/down from critical.