NC program for milling a tapered external thread. This program is arranged so that first another program is called to pre-mill the taper. At the beginning of this called program you have to define all required parameters from which the control then calculates and executes the tool paths to manufacture the taper. After the program call in the main program, you also have to define the parameters required for milling the thread. The control then uses these values to calculate the tool path for the thread. This path consists of linear segments for which the control calculates the X, Y and Z coordinates of each of the end points and then moves to them. Machining is always in the negative Z direction so that you can use the rotational direction of machining to specify whether the thread is left-handed or right-handed.