Gas supply tube and method of making same

A method of making a metal gas supply tube, said method comprising the steps of:

• (a) forming an extremity of a metal tube with a bending-deformed bent region adjacent a rear side of a bending-deformation-free front free end region of the tube;
• (b) inserting said tube into a correspondingly shaped cavity of a forming die so that said front free end region projects from said and an adjoining region of the bending-deformed bent region of said tube extends forward into an enlargement of the cavity having an inner contour corresponding to an ultimate outer contour of a finished circularly cylindrical socket-like enlargement to be provided on said tube;
• (c) forcing an enlarging tool into said free front end region and thereby forcing the adjoining region into said enlargement of said cavity and shaping said adjoining region to said inner contour while a front portion of said tube remains outside said cavity of said die;
• and
• (d) thereafter completing the shaping and sizing of said tube by forcing a calibrating mandral into said front free end region such that only a back end region of said finished circularly cylindrical socket-like enlargement is shaped from a part of the bending-deformed bent region while a front region of said finished circularly cylindrical socket-like enlargement extending from said back end region to said front free end region is shaped from the bending-deformation-free front free end rsegion of the tube.