PURPOSE: To completely pierce without causing end clogging and defective piercing by piercing while pushing the rear end of base stock again with a pusher just before the end of piercing.

CONSTITUTION: Just before the end of piercing, the pusher 5 is again advanced, its tip part 5-1 is brought into contact with the rear end of the base stock 1 and simultaneously the base stock 1 is pushed in between rolls 2 by applying pressure. At this time, the tip part 5-1 of the pusher 5 is revolved in one body with the base stock 1 by the action of a thrust bearing 5-2 and the base stock is completely pierced to the rear end. The pusher 5 is retreated at the same time of the completion of piercing and waited in the home position.