| 摘要 |
<p>A steel pipe (1A) (hollow material) both ends of which are open and having a processing wall portion (5) in which a rack is formed with the tooth die (14c) is held in a die assembly (13) having a tooth die (14c). With a first metal core push rod (31) which is to be inserted/removed into/from the steel pipe (1A) through an opening (2) at one end and a second metal core push rod (35) which is to be inserted/removed into/from the steel pipe (1A) through an opening at the other end, a metal core (25) disposed on a side on which the first metal core push rod (31) is inserted/removed into/from the die assembly (13) is sandwiched and this metal core (25) is stopped from rotating with the first metal core push rod (31). With the state of stopping the rotation of the first metal core push rod, the metal core (25) is introduced into the steel.pipe (1A) through the opening (2) at the one end by both the metal core push rods (31, 35). After the metal core (25) is pressed into the steel pipe (1A) while stopped from rotating with the first metal core push rod (31), this metal core (25) is pushed back by the second metal core push rod (35). Consequently, the flesh of the processing wall portion (5) adjoining the tooth die (14c) is fluidized plastically outward from inside of the steel pipe (1A) so as to form a rack corresponding to the tooth die (14c).
</p> |
