A drilling machine performs a feed operation while rotating a spindle, suspends the feed operation of the spindle for a predetermined dwell time at a predetermined hole bottom position, and then performs drilling by retreating the spindle. A controller for controlling the drilling machine calculates the dwell time based on a prescribed rotation amount in response to specification of the prescribed rotation amount (dwell rotation amount) at the hole bottom position.

A drilling machine performs a feed operation while rotating a spindle, suspends the feed operation of the spindle for a predetermined dwell time at a predetermined hole bottom position, and then performs drilling by retreating the spindle. A controller for controlling the drilling machine calculates the dwell time based on a prescribed rotation amount in response to specification of the prescribed rotation amount (dwell rotation amount) at the hole bottom position.

Provided is a numerical control device that eliminates the need for rapid acceleration/deceleration of a cutting tool during boring and that is capable of minimizing vibration of a machine tool. This numerical control device comprises: a deep hole boring execution unit which performs deep hole boring by repeating a cutting operation for making a cut in a workpiece while rotating the cutting tool and a cutting halting operation for halting the cutting operation of the workpiece while rotating the cutting tool; and a chip-discharging time calculation unit which calculates a chip discharging time depending on the position of the cutting tool after each cut during the cutting operation. The deep hole boring execution unit performs the cutting halting operation during the chip-discharging time.