The invention relates to a device for preparing the end faces of thin-walled jackets for welding, comprising a housing (1), on which an annular separator (2) is mounted, said separator containing at least two groups of elongated deformation elements (4, 6). The longitudinal axes of the deformation elements (4) of a first group are aligned radially in relation to the central axis of the separator (2) and the longitudinal axes of the deformation elements (6) of a second group are aligned at an acute angle (α) in relation to a radial through the central axis of the separator (2).