Abstract: A method and apparatus by which accurate correction values for thermal displacement is calculated even when the rotation of the main spindle is restarted after interruption. The apparatus has means 2, 3 for measuring the temperature near the main spindle 15, means 5 for estimating the thermal displacement of the main spindle 15 on the basis of the measured temperature and a predetermined thermal displacement calculation expression, means 7 for calculating the correction value, and means 6 which estimates the displacement delay in re-rotation caused by the interruption of the rotation of the main spindle 15, and calculates an adjusting displacement on the basis of the estimated displacement delay. The correction value calculating means 7 calculates a correction value on the basis of the thermal displacement estimated by the thermal displacement estimating means 5 alone when the main spindle 15 is started up and rotated.

Abstract: The present invention relates to a method and apparatus for calculating a correction value for thermal displacement whereby accurate correction values for thermal displacement can be calculated even when the rotation of the main spindle is restarted after interruption thereof, wherein the apparatus for calculating the correction value for thermal displacement comprises temperature measuring means 2 and 3 for measuring the temperature in the vicinity of the main spindle 15, thermal displacement amount estimating means 5 for estimating an amount of thermal displacement of the main spindle 15 on the basis of the measured temperature and a predetermined thermal displacement amount calculation expression, correction value calculating means 7 for calculating the correction value, and adjusting displacement amount calculating means 6, which estimates an amount of displacement delay in re-rotation caused by the interruption of the rotation of the main spindle 15, and calculates an adjusting displacement amount on the