Machine tool control device, and machine tool

A machine tool control device for controlling a machine tool that performs turning by rotating a turning axis provided with a holder that holds a workpiece, the machine tool control device comprising:

• an in-aggregate turning inertia estimation unit configured to estimate in-aggregate turning inertia based on feedback from the turning axis by causing the turning axis to rotate, the in-aggregate turning inertia being possessed by an aggregate of the turning axis and an object rotating together with the turning axis and being around the turning axis;
• a workpiece turning inertia estimation unit configured to estimate workpiece turning inertia based on the in-aggregate turning inertia that is present when the holder does not hold the workpiece and the in-aggregate turning inertia that is present when the holder holds the workpiece, the workpiece turning inertia being possessed by the workpiece and being around the turning axis;
• a maximum rotation number calculation unit configured to calculate, based on the workpiece turning inertia, a maximum rotation number of the turning axis such that at the maximum rotation number calculated, maximum energy of the workpiece at a time of detachment of the workpiece from the holder becomes equal to a preset upper limit value;
• and
• a rotation number limiting unit configured to limit a rotation number of the turning axis so as to prevent the rotation number from exceeding the maximum rotation number.