Numerical controller having cutting in/out motion inserting function or circular motion inserting function

A numerical controller configured to control a machine tool according to a machining program, the machine tool performing lathe-turning machining in which a cutting tool moves in contact with a rotating workpiece to form the workpiece into a desired shape, the numerical controller comprising:

• a processor configured to:
• analyze operation conditions for circular motion instructed in the machining program;
• insert and remove the circular motion that is generated based on the analyzed operation conditions into the lathe-turning machining;
• and
• insert the circular motion, of which the tangential speed is the same as the feeding speed for cutting in the location where the circular motion is inserted during the lathe-turning machining, into the lathe-turning machining,
• wherein a circular motion execution flag exec_f represents whether the circular motion is being executed, and
• the circular motion is inserted into the cutting of the workpiece to allow the workpiece and the cutting tool to separate from each other to efficiently cool the cutting tool and address reduction of service life of the cutting tool.