Numerical control apparatus

A numerical control apparatus for a machine tool that performs tapping with a spindle and a feed axis being synchronized with each other, the numerical control apparatus comprising:

• a numerical control unit that interprets a tapping program and outputs a position command value of the spindle;
• an acceleration learning block that calculates and outputs a command acceleration of the spindle during tapping;
• an acceleration/deceleration processing unit that applies an acceleration/deceleration process to the position command value input from the numerical control unit based on the command acceleration input from the acceleration learning block to calculate a post-acceleration/deceleration position command value;
• a position control unit that calculates a speed command value based on the post-acceleration/deceleration position command value input from the acceleration/deceleration processing unit;
• a speed/torque control unit that calculates a motor torque command value from the speed command value input from the position control unit;
• and
• a current control unit that calculates a motor current value of a spindle motor from the motor torque command value input from the speed/torque control unit,
• wherein the acceleration learning block outputs, as the command acceleration, an initial command acceleration which is smaller than the command acceleration which is calculated, in accordance with a state quantity of the spindle motor, to the acceleration/deceleration processing unit.