Patent ID: 8141405

Claim:
A method for producing an ultra thin wall metallic tube of 3.15% or less in percent of wall thickness to diameter (wall-thickness/diameter) with a cold drawing process in which a drawing machine is used, the method comprising: using a solid die which has a surface that contacts a mother tube, the surface having a caliber and comprising a working zone as a wall reducing zone, the working zone at least ranging from a length-wide midpoint of the solid die surface to a finishing exit wherein a portion of the caliber at least in the working zone is configured to gradually increase from an engaging entry side thereof to a finishing exit side thereof; inserting a mother tube into the solid die, the mother tube being expanded at its one end; inserting a plug or a tapered mandrel bar into the mother tube, the plug or tapered mandrel bar being configured such that a diameter thereof gradually increases from the engaging entry side of the solid die toward the finishing exit side of the solid die; and drawing the mother tube from the engaging entry side toward the finishing exit side while a portion where the tube end is expanded is chucked, thereby reducing a tube wall thickness to perform elongation with an elongation rate of at least 1.36 or more while a diameter of the mother tube is being expanded between the solid die and the plug or tapered mandrel bar.