PURPOSE: To facilitate processing, suppress wear, and prolong lifetime by fitting a head system to be provided on a boring rod in a head sleeve to hold a bit with the aid of a key or spline, and restraining the idle rotation.
CONSTITUTION: The boring rod 6 of a rock boring machine is fitted at the tip with a head stem 12. and a head sleeve 13 is fitted on the head stem 12 in such a way as slidable in axial direction and incapable of relative rotating. A preceding bit 17 is fited on the foremost extremity of this head sleeve 13, and a wing bit 21 is provided which is held with possibility of diametric enlargement and shrinkage. At the time of boring, the wing bit 21 is overhung outermore than the periphery of the preceding bit 17, and is set innermore than the bit periphery when the boring rod 6 is retreated. Therein the head stem 12 and head sleeve 13 are restrained so as not to rotate relatively with an axially stretching key 32 or spline in confronting the outside surface of the stem 12 and the inside surface of the sleeve 13. This enables the fit part 12a to be formed equipped with a circular section, and rattles of the fit part 12a can be lessened.
KUNITAKE SEIJI
TSURUTA RYUJI
