PURPOSE: To obtain a hollow needlelike article of good concentric working accuracy of a through hole and outer periphery by drawing the hollow pipe stock subjected to pipe making in the small pipe having a through hole, enlarging the through hole by inserting a drill and grinding after hardening and annealing.
CONSTITUTION: A material is heated at working temp. by preventing the generation of the surface scale of a steel billet by subjecting a heating furnace to atmospheric controlling and made a hollow blank by piercing press. After reheating it by putting into an induction heating furnace a pipe stock 10 is made by an extrusion press. The thickness of the pipe stock 10 is thinned as well as reducing its diameter by inserting it between a cylindrical die 12 and cylindrical plug 11 and drawing with cold working by a chuck 13. The long pipe stock 10 formed in a small pipe is then out in the specified length after its centering, levelling and grooving onto the outer periphery, etc. The cut pipe stock 10 is held by a collect chuck 25 to pierce along the hole of the pipe stock 10 by a drill 27. And after hardening and annealing the surface is subjected to grinding.
Sase, Kazuhiko
Ueda, Nobuhiro
Mutou, Suginosuke
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