Hydraulic bending machines are employed to bend sheets of different thickness to obtain cylinders and cones. Modifying the position of their motor rolls, variable diameters can be obtained. The bending process may need 2, 3 or 4 rolls bending machines. 2 rolls bending machines are suitable for thin sheets in order to rapidly close small ferrules . To bend medium-heavy sheets, 3 rolls bending machines are used, since they permit great flexibility and an easy use. CNC 4 rolls consent the highest precision for the bending process with great operating speed. By means of vertical and lateral supports, even more difficult and specific bends can be obtained. On the contrary, for section bending, it's necessary to use 3 rolls machines with horizontal or vertical axes, that, thanks to digital readouts, can assure the maximum precision in revealing the position of the bending rolls.