Abstract: A device is described for joining metal sheets with a male and female die, of the type in which the dies interact to cut or slice through the sheets to form portions of material which are spread via material flow by the die interaction to prevent separation of the sheets. The female die has plates which provide counter-edges which interact with the male punch to provide the desired cutting. The metal plates are leaf springs which yield after the cutting to permit spreading of the material.

Abstract: A tool for forming a lateral opening in a tube comprises an assembly which can be inserted longitudinally into a tube until it lies opposite to an opening (12) through which an operating member (44) can be passed for operative engagement with the assembly at 46. The assembly includes a wedge member (16) with wedge surfaces (22) extending symmetrically in relation to the direction of motion of the operating member (44). Two spreader bodies (28,30) are mounted on the wedge member (16) and after initial insertion of the tool the operating member acts to displace the wedge member and hence the spreader body so that it contacts and deforms the interior of the pipe. Complete withdrawal of the tool through the opening (12) deforms the metal surrounding the opening and after a suitable finishing process another tube can be welded at right angles to the first mentioned tube to form a T-piece.