Machine tool and control method and control program thereof

A method for controlling a machine tool comprising:

• a spindle rotatably holding a cylindrical workpiece;
• a turret holding a thread whirling tool having a cutter ring having a base on which a through hole is formed and a plurality of types of cutting tools disposed on the inner diameter side of the base, the plurality of types of cutting tools including a first cutting tool for forming a first screw groove by cutting the workpiece, and a second cutting tool having a shape different from that of the first cutting tools for forming a second screw groove by cutting a workpiece, so as to rotatably hold the cutter ring;
• a controller controlling rotations and relative movements of the spindle and the turret, wherein the controller executes a process to
• have the spindle hold the workpiece,
• disposes the workpiece in the through hole so that the workpiece penetrates the through hole,
• rotate at least one of the cutter ring and the workpiece, and
• switches movements of the thread whirling tool in an extending direction of the workpiece and a direction intersecting with the extending direction thereof, depending on whether the first cutting tool is forming the first screw groove or the second cutting tool is forming the screw groove.

A computer readable non-temporary recording medium having stored therein a computer program for controlling a machine tool comprising:

• a spindle rotatably holding a cylindrical workpiece;
• a turret holding a thread whirling tool having a cutter ring having a base on which a through hole is formed and a plurality of types of cutting tools disposed on the inner diameter side of the base, the plurality of types of cutting tools including a first cutting tool for forming a first screw groove by cutting the workpiece, and a second cutting tool having a shape different from that of the first cutting tools for forming a second screw groove by cutting the workpiece, so as to rotatably hold the cutter ring;
• a controller controlling rotations and relative movements of the spindle and the turret, wherein the controller executes a process to
• have the spindle hold the workpiece,
• disposes the workpiece in the through hole so that the workpiece penetrates the through hole,
• rotate at least one of the cutter ring and the workpiece, and
• switches movements of the thread whirling tool in an extending direction of the workpiece and a direction intersecting with the extending direction thereof, depending on whether the first cutting tool is forming the first screw groove or the second cutting tool is forming the screw groove.