Turning process method for workpiece and machine tool

A turning method for machining a step-shaped workpiece, the step-shaped workpiece including a small diameter portion and a large diameter portion continuous with the small diameter portion, the turning method comprising:

• feeding a tool that includes an insert with a main cutting edge having a straight portion in either a rotation axis direction of a workpiece or a radial direction of a workpiece or both directions while rotating the workpiece;
• using a machine tool having a pivot shaft of the tool in the machine side;
• machining a peripheral surface of the small diameter portion by turning the pivot shaft so as to have a cutting edge angle of less than 90°, the cutting edge angle having an angle between the straight portion of the main cutting edge and the rotation axis direction;
• and
• machining an end surface and a peripheral surface of the large diameter portion by turning the pivot shaft so as to have the cutting edge angle of 90° or more at a front of the large diameter portion.