Method and parts for making a tubular workpiece, in particular a built-up camshaft

A method of hydroforming a tubular built-up camshaft, the method comprising the steps of sequentially:

• providing a support tube having one end with a predetermined outer diameter;
• providing an end piece formed with a cavity and having
• a front end at which the cavity opens,
• a front portion at the front end and of a front inner diameter that is larger than the outer diameter of the one end of the support tube, and
• a rear portion rearward in the cavity from the front portion of a rear inner diameter that is smaller than the outer diameter of the one end of the support tube, the front and rear portions forming a step defining a circumferential edge;
• relatively displacing the support tube and the end piece so as to insert the one end of the support tube into the cavity of the end piece and move the support tube relative to the end piece starting from the front end of the cavity rearward toward the rear portion such that the circumferential edge cuts into the support tube;
• and
• expanding the support tube radially outward against the end piece by internally pressurizing the cavity with a fluid.