Abstract: The invention relates to an apparatus for mechanically joining metal sheets which lie flat one upon the other, having a tool set comprising at least one punch and one die which bounds a cavity in which the joining operation takes place, the punch displacing sheet-metal material out of a sheet-metal plane and upsetting it, and at least one tool part being arranged, for this purpose, on a displaceable tool carrier which has a holding-down means supported in a spring-prestressed manner adjacent to the tool part. In order that the holding-down means allows high outputs, it is provided that, for the spring prestressing of the holding-down means, the tool carrier has a cylinder cavity in which there is guided a piston which acts on the holding-down means and on the head side bounds, with volume-changing action, a pressure chamber which can be subjected to the action of a fluid pressure medium.

Abstract: Method for the local forming of material tending towards brittle fracture, such as certain aluminum alloys, in which during the forming tensile loads are exerted on the material, such as for example in joggle joining. Brittle fracture is avoided if the material is subjected to a pressure load in the region which is to be formed.