Patent ID: 8532813

Claim:
A method of controlling thread cutting, comprising the steps of, performing thread cutting in work held on a main spindle with a tool by transferring the tool in the direction of a Z-axis parallel to an axis of the main spindle in synchronization with rotation of the main spindle, and after the thread cutting, performing a pullout operation in which the tool is retracted in the direction of an X-axis perpendicular to the axis of the main spindle, the tool being accelerated and decelerated under acceleration/deceleration time constant control whereby feed shafts reach a maximum allowable speed in a prescribed acceleration/deceleration time Ta, wherein in the pullout operation, a speed command Ve for causing an acceleration in the direction of the X-axis to be greater than an accelerational under the acceleration/deceleration time constant control and smaller than an allowable acceleration α 2 in the direction of the X-axis is issued during command time Te when an actual speed of the tool in the direction of the X-axis remains at or below an allowable maximum speed Vmax in the direction of the X-axis and, subsequently, a speed command of value zero is issued until the prescribed acceleration/deceleration time Ta elapses under the acceleration/deceleration time constant control so as to control the acceleration in the direction of the X-axis during the pullout operation.