Machine tool with automatic tool changer, and eddy current sensor used for same

A machine tool with an automatic tool changer configured to mount a tool holder to which a tool is attached on a spindle head and rotationally drive the spindle head to machine a workpiece, the machine tool with the automatic tool changer comprising:

• an eddy current sensor disposed such that a measurement end surface faces an outer peripheral surface of a flange of the tool holder;
• and
• a data processor configured to detect runout of the tool mounted on the spindle head based on data obtained by measurement by the eddy current sensor, wherein the eddy current sensor comprises:
• a coil formed in a spiral shape and held in a bobbin serving as a cylindrical container;
• and
• a core serving as a soft magnetic body disposed at an axial center of the coil on the measurement end surface side,
• wherein a ratio of a core length that is an axial length of the core to a coil length that is an axial length of the coil (core length/coil length) is 1.35 to 1.65.

An eddy current sensor used to detect runout of a tool mounted on a spindle head of a machine tool with an automatic tool changer, the eddy current sensor comprising:

• a coil formed in a spiral shape and held in a bobbin serving as a cylindrical container;
• and
• a core serving as a soft magnetic body disposed at an axial center of the coil on a measurement end surface side, wherein
• a ratio of a core length that is an axial length of the core to a coil length that is an axial length of the coil (core length/coil length) is 1.35 to 1.65.