Sharpening device for rotating cutting tools and machine employing said device

A log severing machine for cutting rolls or logs of web material into small rolls, comprising at least one rotating discoidal cutting tool and an associated sharpening device, said sharpening device comprising at least two sharpening grinders located on opposite flanks of said discoidal cutting tool, wherein each grinder of said at least two grinders is provided with a corresponding dressing tool which interacts with said grinder to dress a working surface of said grinder, and wherein each said dressing tool has a first actuator for moving said dressing tool alternately into an active position, in which said dressing tool acts on said grinder, and into an idle position, in which said dressing tool is withdrawn from the grinder.