This invention concerns a tool with at least one wear-resistant hard metal part which serves to process production pieces, such as stone or the like, which is firmly connected to a metallic carrier by means of solder located in at least one soldering aperture between the hard metal part and the metallic carrier. Among such tools are bits, such as drill bits, turning tools, and the like and processing tools to remove shavings, from lathing, milling, and the like.
Hard metal has a substantially smaller coefficient of expansion than a carrier consisting mostly of steel. Even during the soldering of the hard metallic part to the carrier, strains arise between the hard metallic part and the carrier. Because of the forces and temperature increases which may occur during operation, the strain may increase still further, and often causes tension cracks in the hard metal part, and thus causes failure of the tool.
Using a soft solder to reduce the danger of the formation of tension cracks is known. This solder connection is, however, not sufficient in many cases, especially for high performance tools. Thus, hard solder is preferred.
The greater the cross section and length of the hard metal part, the greater is the danger of tension cracks in the hard metal part. Even in high performance tools, the hard metal part must be supported in the carrier over a large surface area, in order to be able to absorb the considerable forces and momentum.