Abstract: A hollow metal tube having a sharp-angled indentation that is made without removing any material and without deforming the external diameter while conserving the fiber orientation of the metal and maintaining a constant thickness of the tube. The process of forming the sharp-angled indentation comprises the steps of, providing a riveting machine, the riveting machine having an epicycloid mechanism and a spherical joint and comprising a riveting head fitted to a spindle, operating in conjunction with pressing devices and a fixed half-clamp, replacing the spindle of riveting machine with a sharp angled former adapted to the profile of the indentation to be made and to the former's sharp angle, inserting the tube on which indentations are to be made between the former and the fixed half-clamp, and activating the pressing devices to cause movement of the spindle in order to form the sharp-angle indentation in the tube.

Abstract: A process by which it is possible to make a sharp-angled indentation on hollow tubes without removing any material, maintaining a constant thickness of tube and also without deforming the external diameter and conserving the fiber orientation of the metal, characterized by the fact that a riveting machine is used, which itself is a well-known type of machine, comprising a riveting head fitted to a spindle operating in conjunction with pressing devices and a fixed half-clamp. The riveting head of this machine is replaced by a former adapted to the profile of the indentation required and in particular to its sharp angle. The tube in which indentations are required (1) is positioned between the former and the fixed half-clamp and the pressure devices are operated, causing movement of the spindle in order to allow indentation of the tube (1).