To provide a control device for a machine tool capable of properly holding a workpiece, even when holding force of a holding member is lowered.
In this machine tool, a chuck 8 is provided with a slide member 25 movably and drivably in a shaft center CT2 direction, and the workpiece 7 is fixed and held by using the chuck 8 by projecting a workpiece holding member 25g in the shaft center CT2 direction and moving the slide member 25 in the shaft center CT2 direction by driving a reciprocating and driving means 42. The machine tool is provided with a sensor 42d for detecting the release of the fixed and held state of the workpiece 7 by the workpiece holding member 25g during rotation of a main shaft 9, and driving and control means 46 and 50 for driving the slide member 25 in the shaft center CT2 direction (an arrow D direction) by the reciprocating and driving means 42 when detecting the release of the fixed and held state of the workpiece 7. Even when holding force such as hydraulic pressure of the workpiece holding member 25g is lowered, lowering of holding force of the workpiece 7 can be prevented to the utmost by moving the slide member 25 in the shaft center CT2 direction, that is, a workpiece direction.
KOIKE HARUHIKO
YAMAMOTO NOBORU
