Musashi Seimitsu Industry Co., Ltd.

Yasuyoshi Matsui

Shinichi Murata

Shinji Ieki

An upper die and a lower die are brought together to perform a sizing work on a roughly forged part of a primary forged article within a die cavity defined between the upper and lower dies. The lower die has a vertical through-hole directly communicated with the die cavity, and a punch is relatively movably received in the vertical through-hole in such a manner as to define jointly with the vertical through-hole an annular material flow passage. During the sizing process, a material of the roughly forge part is forced against a peripheral surface of the die cavity and excess material is allowed to flow into the annular material flow passage.

Forged material sizing method and apparatus

The present invention is a method of forging a bevel gear, comprising: a first forging step in which a first intermediate article is obtained by pressing a blank, such that there is formed a preliminary one-end recessed part that is axially recessed in an axis-center part on an axially one-end side and/or a preliminary other-end recessed part that is axially recessed in an axis-center part on an axially other-end side; a second forging step in which a second intermediate article is obtained by pressing the first intermediate article in a hermetically sealed cavity space defined by a first die and a second die that is positioned opposedly to the first die in the axial direction, such that there are formed: a body part including a tooth part on a radially circumference thereof and a one-end recessed part that is axially recessed in an axis-center part on the axially one-end side; and a projecting part projecting from a rear surface part of the body part on the axially other-end side; and a through-hole forming step in which a bevel gear having a through hole in an axis-center part is formed by removing the axis-center part extending from a bottom surface of the one-end recessed part to the projecting part of the second intermediate article. The tooth part provides a tooth-crest surface which is tapered from the axially other-end side to the axially one-end side, and upon completion of the second intermediate article in the second forging step, there remains an unfilled space between the projecting part of the second intermediate article and a wall surface of the dies defining the cavity space.

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Toyohashi, Japan

Yasuyoshi Matsui