Abstract: A hard metal of WC for tools for mechanical working of stone, concrete, and asphalt conatins 5 to 25% by weight of a binder based on Co or Co and Ni. The hard metal has a coercive field strength up to 17.0 kA/m, and the binder contains up to 30% of Fe. The hard metal has a magnetic saturation (? or 4??, in units of microtesla times cubic meter per kilogram, respectively) as a function of the Co proportion (X) in % by weight of the hard metal in a range of ?=0.11 X to ?=0.137 X or 4??=0.44 ? X to 4??=0.548 ? X.

Abstract: The present invention provides a roller bit for tunnel-driving machines. Pursuant to the invention, a cutting ring has at least two or more segments. Accordingly, it is possible to renew the cutting ring itself or different parts of the cutting ring segment by segment, without the previously required dismantling and installation of a complete roller bit from a drill head and associated expenses of transporting. A total driving time is thus reduced because of shorter repair times. The segments of the cutting ring are disposed in a fixed position preferably by means of profiled guides on the base roller body and connected with the base roller body by means of segment holding devices which have a screw thread, and/or by means of threaded rings.