Form rolling apparatus and form rolling method

A form rolling apparatus for applying in-feed form rolling to an outer periphery surface of a rod-shaped material to generate helical gear teeth, the form rolling apparatus comprising:

• a support portion configured to support the rod-shaped material to be axially rotatable;
• a round die formed with die teeth on an outer periphery thereof, the round die being rotatable about a rotational axis which is configured to be arranged in parallel with an axial direction of the rod-shaped material configured to be supported by the support portion, the die teeth configured to be positioned facing the outer periphery surface of the rod-shaped material configured to be supported by the support portion;
• a rotation drive device rotationally actuating the round die;
• and
• a moving device moving the round die in a direction orthogonal to the rotational axis of the round die so that a distance of axes of the round die and the rod-shaped material changes;
• wherein the die teeth includes forming die teeth for generating the gear teeth on the outer periphery surface of the rod-shaped material and finishing die teeth enhancing a tooth surface precision of the generated gear teeth by engaging with the generated gear tooth and rotating;
• and
• wherein the finishing die teeth each have an addendum region that is less than an addendum region of the forming die teeth by a predetermined length.