Patent ID: 6725698
Filing Date: 2004-04-27
Classification: B21D

Abstract:
A method of forming, on an end portion of a tube stock, a tip reduced portion having a circular configuration in section which is gradually reduced in diameter from a center side of said tube stock towards an end edge side of said tube stock comprising the steps of:relatively rotating a forming tool about an axis of said tube stock; moving said forming tool towards the axis of said tube stock as said forming tool is moved from the center side of said tube stock towards the end edge side thereof while pressing said forming tool against an outer periphery of the end portion of said tube stock, which outer periphery has a sectional configuration having different lengths in two orthogonal directions with respect to the axis of the tube stock; and forming said tip reduced portion of said tube stock such that an angle of inclination of an outer periphery of said tip reduced portion with respect to the axis of said tube stock is gradually reduced from the center side of said tube stock towards the end edge side of the tube stock so that a generating line of the outer periphery of said tip reduced portion becomes in final form a center recessed curve and reduced short axis projections are formed.