a riveting device for the assemblage of two or more sheet metal sections of a structure comprising a working unit operable on one side of the sections to be assembled and a clamping and bucking unit operable one the opposite side of the sections . both units comprise clamping means respectively , by which the sections are clamped together during the entire working cycle in each rivet position , i . e . during hole making , seal compound application , rivet insertion and rivet upsetting . the clamping means of the bucking unit comprises a head , one or more low inertia contact elements and a resilient impact absorbing means provided between the contact element or elements and the head . the combination of a low inertia contact element and a resilient impact absorbing means provides a solution to the problem of reducing the extremely high contact forces generated at each blow from the riveting tool between the clamping means on the bucking side and the sheet metal sections . deformation of the sections due to such high forces is thereby avoided .