Device for controlling machine tool

A machine tool comprising:

• a first linear motion axis, a second linear motion axis, and a third linear motion axis of a machine coordinate system which are orthogonal to each other;
• a first rotary feed axis about a first axis line inclined with respect to all linear motion axes of the first linear motion axis, the second linear motion axis, and the third linear motion axis, the first rotary feed axis and the linear motion axes being configured to move a table on which a workpiece is placed;
• servomotors connected to the first, second and third linear motion axes and the first rotary feed axis;
• a servomotor control unit which drives and controls the servomotors by an instruction based on the machine coordinate system;
• a control device controlling the machine tool based on an instruction of manual operation by an operator in addition to a machining program,
• wherein the control device comprises
• an arithmetic unit which calculates, from a coordinate value of the machine coordinate system, a coordinate value of a table coordinate system including a first virtual linear motion axis, a second virtual linear motion axis, and a third virtual linear motion axis orthogonal to each other with a reference being a workpiece attachment surface of the table and a first virtual rotary feed axis about a first virtual axis line parallel to one of virtual linear motion axis of the first virtual linear motion axis, the second virtual linear motion axis, and the third virtual linear motion axis;
• and
• a display unit which displays the coordinate value of the table coordinate system calculated by the arithmetic unit, the coordinate value of the table coordinate system being a virtual coordinate value which simulates the coordinate value of the machine coordinate system of the machine tool in which the first axis line of the first rotary feed axis is parallel to one of the linear motion axes.