A numerical control unit is provided that can change an override value according to various workpiece materials and can extend the tool life. A numerical control unit includes a variation storage unit that stores a variation in override value of a feed speed or a spindle speed for each workpiece material, an override value setting unit that sets the override value based on the variation in override value according to the material of a workpiece being machined; and a control unit that changes the feed speed or the spindle speed based on the override value.

A controller for controlling a synchronized operation of spindle and feed axes. A spindle-axis control section includes an initial-motion control section for making a spindle axis perform an accelerated rotation at maximum capacity from a process start position; a maximum-acceleration detecting section for detecting a maximum acceleration of the spindle axis; a residual rotation-amount detecting section for detecting a residual rotation amount of the spindle axis; a current-speed detecting section for detecting a current speed of the spindle axis; a positioning-motion control section for making the spindle axis perform a decelerated rotation so as to reach the target thread depth after the accelerated rotation; and an overshoot detecting section for detecting an overshoot of the spindle axis during the decelerated rotation.

A controller for controlling a synchronized operation of spindle and feed axes. A spindle-axis control section includes an initial-motion control section for making a spindle axis perform an accelerated rotation at maximum capacity from a process start position; a maximum-acceleration detecting section for detecting a maximum acceleration of the spindle axis; a residual rotation-amount detecting section for detecting a residual rotation amount of the spindle axis; a current-speed detecting section for detecting a current speed of the spindle axis; a positioning-motion control section for making the spindle axis perform a decelerated rotation so as to reach the target thread depth after the accelerated rotation; and an overshoot detecting section for detecting an overshoot of the spindle axis during the decelerated rotation.