Method of controlling drive of driving motor for rotary indexing device of machine tool

A method of controlling drive of a driving motor for a rotary indexing device of a machine tool, the rotary indexing device including an indexing mechanism that indexes an angular position of a circular table by rotating the circular table with the use of a driving motor as a driving source, a clamping mechanism that holds the indexed angular position, and a control unit that controls the drive of the driving motor by position control, the method being performed by the control unit, the method comprising the step of:

• controlling the drive of the driving motor during operation of the clamping mechanism with a content of control in which an output torque of the driving motor by the position control becomes smaller than an output torque by the position control during indexing of the angular position of the circular table for an equivalent positional deviation.