Patent ID: 6237389
Filing Date: 2001-05-29
Classification: B21D,B21H,B21K,Y10S

Abstract:
An apparatus for forming a screw-thread on a metal pipe, comprising:a plurality of main forming punches adapted to be distributed about an outer periphery of the metal pipe, each of said main forming punches comprising at least one thread forming portion having a radius of curvature substantially equal to a radius of curvature of the screw-thread to be formed, said main forming punches being radially movable with respect to the center of the metal pipe between an open position and a closed position, said at least one thread forming portion of each said main forming punch being adapted to engage the outer periphery of the pipe so as to form the screw-thread when said main forming punches are in said closed position; anda plurality of auxiliary forming punches adapted to be distributed about the outer periphery of the pipe, said auxiliary forming punches being interspersed among said main forming punches, said auxiliary forming punches extending a smaller distance than said plurality of main forming punches along an outer periphery of the metal pipe, each of said auxiliary forming punches comprising at least one forming portion, said auxiliary forming punches being radially movable with respect to a center of the metal pipe between an open position and a closed position independently from said main forming punches, said at least one forming portion of each said auxiliary forming punch being adapted to engage the outer periphery of the pipe so as to at least partially form the screw-thread when said auxiliary forming punches are in said closed position.