Abstract: A process of forming the wall of the mouth of a cylindrical, metal container or packaging from a tubular ring that may or may not be molded that has to accommodate a sealing lid equipped with an elastic seal secured by a vacuum created in the container is characterized essentially by the use of a single element, the head carrying out the deformation of the internal diameter of the container by expansion to produce a bead together and simultaneously with a contraction that produces shrinkage above the bead of the mouth, the head comprising an expansible stationary part and a moving part that turns around the stationary part, the parts of the head being coaxial, which has the effect of compressing the metal and hardening it by organizing the metal molecules under two simultaneous stresses, which hardens the packaging and allows it to withstand the vacuum applied thereto.