Abstract: The balancing machine of the present invention automatically determines the position of unbalance in a rotating part and stops the rotating part with the unbalance position in a predetermined location. Sensors on the bearings holding the rotating part generate signals proportional to the instantaneous unbalance. These signals are filtered and digitized at a sampling rate synchronous with the motor driving the rotation. Two contiguous sets of samples, each set spanning several revolutions of the part, are stored. The X and Y components of the unbalance signal are calculated for each sample set and the actual rotation rate of the part is calculated from the assumed rate and any difference in the phase angle of the unbalance location between the first and second sample sets. These calculations are performed during a calculation interval of predetermined length which follows the sampling.