Tube drawing technique

A method of tube drawing to produce a cold finished stepped internal diameter tube, which comprises:

• positioning within an opening of a die a tube hollow consisting essentially of a section having a uniform outer and stepped inner diameters greater than the outer and inner diameters of the finished tube;
• positioning within the tube hollow a mandrel including a mandrel plug and a mandrel rod connected to the mandrel plug, the mandrel plug having a first cylindrical working surface, a second larger diameter cylindrical working surface and plug means for automatically positioning the first cylindrical working surface and the second cylindrical working surface within the die opening;
• and causing relative movement of the tube hollow with respect to the die, in one draw pass, with the plug means automatically positioning the first cylindrical working surface to reduce the wall of a first portion of the tube hollow section and with the plug means further automatically positioning the second cylindrical working surface to reduce the wall of a second portion of the tube hollow section such that the outer diameter is uniformly reduced and the inner diameters are successively reduced.