The influence of the milling-process on the system-dynamics of a hybrid bearing HPC (high performance cutting) motor spindle is investigated. An additional electromagnetic actuator allows for identification and active vibration control. Semi-discretization is used to calculate the eigenvalues of the motor spindle depending on increasing axial depth of cut. This result is used to design a controller for chatter suppression that accounts for the influence of the process on the system dynamics. The controller increases the critical depth of cut considerably. The results of the semi-discretization as well as the effect of the active damping are validated by experimental identification during slot-milling of aluminum.