Abstract: A staged tool for boring a hole in a heated element of a material such as metal. The tool is adaptable to being axially forced and operation of the tool causes plastic deformation of the bored material. The tool successively includes, beginning at its front end, a front cylindrical or conical end portion having a first relatively small diameter, a neck followed by a working portion of evolving revolution having a right cross-section which increases in the direction of advancement of the tool, whose major base has a second diameter greater than the first diameter. To improve lubrication during boring, positioned on the neck at the rear of the front end portion is a mass of solid lubricant having a fusion point less than the temperature of the element during the piercing operation. The solid lubricant melts when the tool penetrates into the heated element and the contact surface between the element and the working element is constantly lubricated by a melted lubricating film.

Abstract: A guide tube for guiding a wire (23) of filler metal in an arc welding machine and for applying arc current thereto comprises a metal body (80) having a longitudinal bore (82) through which the wire passes. Near the front end of the tube there are two transverse passages (95) housing respective ball (96) which are urged to project into the bore by respective spiral compression springs (97). These serve to keep the wire pressed against the opposite side of the bore to maintain good electrical contact. The springs are held in by a sheath (100) fitted over the end of the tube. The sheath also serves to keep an end piece (50) in place. Both the sheath and the end piece are made of refractory material which is electrically insulating and which is non-adhesive to spattering metal from the weld melt. This helps to prevent the front of the tube getting clogged up in operation.