Abstract: A hydro-pneumatically operated repetition riveting tool, which tool includes a gripping means for releasably gripping an elongated mandrel at a position remote from the mandrel head, which gripping means comprises a housing with an internal taper, and a plurality of mandrel-gripping jaws which are urged into contact with the mandrel by means of the internal taper; hydraulic retraction means for retracting the mandrel, thereby to pull the head of the mandrel through a rivet on the mandrel and adjacent the head, thereby to place the rivet; return means for returning the mandrel forwardly again after placing a rivet; and rivet feeding means for feeding rivets forwardly towards the mandrel head; in which the return means is pneumatically powered; and in which the housing of the gripping means comprises a first part and a second part, spring means for urging the first and second parts relatively apart from each other, and limiting means for limiting the movement apart of the first and second parts under the urging