PURPOSE: To prolong the life of dies and to manufacture a fine half hollow material at the neighborhood of openings by forming clearance between a tong formed part and a joint part and joining both of them with a joint member through the clearance as a forming die and a reinforcing die are assembled.
CONSTITUTION: A metallic half hollow material such as aluminum is extruded by a die 2 made up by assembling the forming die 3 and reinforcing die 4. In that case, the joining condition of a bolt 5 is adjusted and a shearing force of a certain extent can be given to a base end contracted part 8a of a tong formed part 8 in advance by use of clearances 22, 22a in the direction opposite to the shearing force given by an extruding pressure in time of extrusion. Therefor, though the pressure of the extruding material acts on the base end part 8a of the tong formed part 8 at the time of extrusion, the base end part can bear it, damages at the base end part of the tong formed can be reduced and the life of the dies can be increased. Further, since the tong formed part 8 is formed integrally with the forming die 3 through the base end part, no burrs are formed at the opening part of the tong.
OTA YUKIHIKO
TANIGAWA MASAKAZU
