Abstract: A spark erosion machine tool is equipped with a drive head carrying, at an angle to its moving direction, a plurality of drive slides, with a stationary work piece holder, and with a plurality of movable spark erosion electrode mounting bucks. The drive slides (4) cooperate with the mounting bucks (20) for converting the movement of the drive head into a movement of the spark erosion electrodes. For example, when the drive head is a ring, its axial movement relative to a round work piece, such as a combustion chamber of a jet engine, is converted into radial movements of the erosion electrodes for plunge cutting cooling slots or openings into the outer jacket of the combustion chamber. Thus, many slots can be cut simultaneously. The movable mounting bucks (20) carry electrode holders (16) and the bucks are movably supported on guide rods (25) in the stationary work piece holder. The electrodes with their holders are guided in slots (14) of the work piece holder.

Abstract: Structural parts, particularly of complicated shape, are diffusion welded to each other under isostatic pressure to form permanent joints. A two phase operation is involved in the joint formation. In the first phase at least one of the welding joint forming surfaces of the two parts to be joined, is provided with a material which will form a metallurgical layer in the gap between the two surfaces forming the welding joint. The metallurgical layer forming material may be applied to one or both joint forming surfaces prior to assembly of the parts or the material may be introduced into the gap between the surfaces after the parts have been assembled. In both instances it is the aim to seal the gap prior to the second phase in which a diffusion welding is performed in a hot isostatic press.