Machine tool provided with spindle having measurement function

A machine tool comprising:

• two spindles one of which is a hollow spindle including a hollow portion along an axial direction;
• a plurality of chuck claws openably mounted at a distal end portion of the hollow spindle, and configured to hold a holding portion of a workpiece;
• an operation rod inserted into the hollow portion of the hollow spindle in a movable manner, and configured to close the plurality of chuck claws with movement of the operation rod toward one side in the axial direction and open the plurality of chuck claws with movement of the operation rod toward the other side in the axial direction;
• a measuring apparatus configured to measure an opening dimension of the plurality of chuck claws based on a movement amount of the operation rod, and configured to measure a processed dimension of the holding portion simultaneously with holding the holding portion with the plurality of chuck claws;
• and
• a comparison unit configured to judge a quality of the processed dimension by comparing a measured value of the processed dimension with a value registered in a storage unit,
• wherein the measuring apparatus includes
• a stroke sensor configured to detect the movement amount of the operation rod,
• a calculation unit configured to convert the movement amount of the operation rod into the opening dimension of the plurality of chuck claws, and
• a correction unit configured to cause a detection value detected by the stroke sensor to be linearly approximated to make a correction.