Abstract: A necking-out tool for forming cylindrical nipples or necks on the circumferential surface of pipelines, containers and the like. The tool is provided with a screw plug having a hook-shaped forming head and a thrust sleeve fitted with a coaxial downholder flange cooperating with the forming head and the screw plug. The thrust sleeve has a hollow cylindrical interior corresponding to the forming head for the reception of the formed neck. A holding appliance resembling tongs is connected to the downholder flange and the thrust sleeve by a hinge. The holding appliance is adapted to be applied at right angles or from the side of the pipeline. One jaw of the tongs terminates at the hinge and the other jaw forms a trough-shaped support for the pipeline on the side opposite the hinge.