Patent ID: 8677797

Claim:
A method for manufacturing a hollow rack comprising: holding a metallic hollow material having a processing wall portion in which a rack is to be formed by means of a tooth die within a die assembly having the tooth die; with a first metal core push rod which is inserted into and then removed from the hollow material through an opening at one end of the material and a second metal core push rod which is to be inserted into and then removed from the hollow material through an opening at the other end, sandwiching a metal core disposed on only a side in which the first metal core push rod is inserted into and then removed from the die assembly, preventing rotation of the metal core at least with the first metal core push rod, and with the rotation of the metal core prevented, introducing the metal core into the hollow material from the opening at the one end by both the metal core push rods; after pressing the metal core into the hollow material with the rotation of the metal core prevented by the first metal core push rod, pushing back the metal core by the second metal core push rod while sandwiching the metal core between the second metal core push rod and the first metal core push rod; and plastically fluidizing a fabric of the processing wall portion adjoining the tooth die outward from inside of the hollow material so as to form a rack corresponding to the tooth die, wherein an end formed into the rotation stop face of the metal core is formed in a convex face or a concave face extending in a thickness direction or width direction of the metal core while a front end formed into the rotation stop face of the first metal core push rod is formed into the concave face or convex face extending in the thickness direction or width direction of the first metal core push rod and wherein both ends is formed into the concave face or convex face extending in width direction of the metal core.