ball mill Bull gear is 2-piece split design. TABLE 1 - BALL MILL SHAFT SPEEDS, EXPECTED FORCING & FAULT FREQUENCIES BALL MILLS, FORCING FREQUENCIES (CPM) SHAFT SPEEDS 1X RPM MOTOR SPEED 1,191 BALL MILL PINION SPEED 226 BALL MILL GEAR SPEED 18 GEARBOX (Between Motor & Ball Mill) NB FTF BSF 2X BSF BPFO BPFI