Fremgangsmåde og anordning til fremstilling af et rør af båndmateriale

摘要

The method of making thin wall metal tubes involves cold forming a thin metal blank into an increasing curved section with the edges (4) closed and then welded together. The partially formed blank (3) is first twisted around a quarter turn and, prior to welding closed, is rotated back slightly. The claims also include a machine for carrying out the method.