Tool drive having a spindle shaft and operating method

Tool drive with spindle shaft for a chip-forming machining, comprising at least one electromagnetic axial actuator and a control and/or regulation apparatus for the operation of the at least one axial actuator for changing the position of the spindle shaft along the longitudinal axis, wherein the control and/or regulation apparatus is designed to drive the at least one axial actuator for the generation of microvibration movement of the spindle shaft, independently of and superimposable on a feed movement, in order to affect chip size and chip shape of removed material created when drilling, wherein at least one axial magnetic bearing and/or one linear motor is provided as at least part of the at least one axial actuator, wherein the control and/or regulation apparatus comprises a memory unit and/or a function generation unit, and is configured to specify setpoint values of the oscillation curve of the microvibration movement depending on geometrical and/or physical data of the workpiece and/or process variables that are measured or determined indirectly and/or control inputs, so that the control and/or regulation apparatus is configured to adjust an axial microvibration movement of the spindle shaft, independently of and superimposed on a feed movement, in such a way as to affect the chip size and chip shape of the removed material created when drilling by adjusting the setpoint value of the oscillation curve of a partial movement section of the microvibration movements at or before the tool contacts the surface of the workpiece to provide a lower feed rate when contacting the workpiece's surface.