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).