Abstract: A punching unit for punching holes of a selected geometry in a wall of a component. The punching unit has a frame for supporting the component and the tool and die assembly releaseably securable to the frame. Tool and die assembly has a punch operatively coupled to a mandrel and a male die member and a female die member cooperating to form the hole in the wall. A portion of the tool and die assembly is interchangeable to provide a selected one of a plurality of predetermined hole geometries for the component.