Method for processing gear and cutter for processing gear

A method for processing a gear, comprising processes of:

• arranging a work rotatably supported about a work axis and a cutter rotatably supported about a cutter axis such that the work axis and the cutter axis are offset from one another;
• synchronously rotating the work and the cutter at a predetermined ratio of an angular velocity;
• operating a first cutting process setting the cutter axis at a first posture wherein a tooth trace direction of a gear-shaped first cutter portion arranged at a first end of the cutter is along a tooth trace direction of the work, setting a first cutting direction wherein the first cutter portion is arranged at a downstream in a moving direction of the cutter in a direction along the work axis, starting the cutting of the work by moving the cutter in the first cutting direction while maintaining a cutting depth of the work, the cutting depth attained by using the first cutter portion, at a setting value, and reducing the cutting depth of the work before the first cutter portion reaches an end portion of a cutting area in the first cutting direction in the process of the cutting of the work;
• and
• operating a second cutting process synchronously rotating the work and the cutter in a reverse direction of rotational directions of the work and the cutter in the first cutting process after the first cutting process, setting the cutter axis at a second posture wherein the tooth trace direction of a gear-shaped second cutter portion arranged at a second end of the cutter is along the tooth trace direction of the work, maintaining the cutting depth of the work, the cutting depth attained by using the second cutter portion, at the setting value, and cutting the end portion of the cutting area by moving the cutter in a second cutting direction, a reverse direction of the first cutting direction.