Abstract: The apparatus for screwing in and out studs (3) of large dimensions, particularly for fastening a cover (2) of a vessel (2) provided with threaded holes, comprises a system (13) which serves to balance the weight of the stud and is force pilot operated by an oleohydraulic means by electrohydraulic feedback control based on accurate measurement of the hydraulic pressure detected at the oleohydraulic means or the balancing load to be exerted by said oleohydraulic means in order to limit the contact pressure between the stud and the threaded hole, and which axially drives, over an adequate path, a mechanism rotationally driving the stud and a means for gripping said stud.