Abstract: The invention concerns a process and a device to form a bung in which a piece (1) is provided that features a protrusion (2) designed to define said bung, said protrusion (2) constituting a conduit (3) equipped with a previously closed first end, with said piece in place in an enclosure (5); said piece (1) is released from said enclosure (5) using relative driving means (6) of one in relation to the other and said previously closed end is unplugged using cutting means (7) operated, directly or not, by said driving means (6). The invention concerns also a fabrication mold for a hollow body, such as a tank, provided with a bung, equipped with the above-described device.