Method and tool for drilling chamber-type holes, particularly in walls made of concrete, plaster or similar material

摘要

Tool for piercing chamber-type holes comprising a blade which may move angularly about a transverse spindle placed at the end of an elongate body and means for varying the inclination of the said blade when an axial thrust is still exerted on the said body in order to move it beyond the point where the tool comes into contact with the bottom of the hole, the said blade L comprising a surface portion Lc shaped so as to act as a cam which interacts with a shaped surface portion of a ball B bearing at the bottom of the hole, the said surface portion Lc of the blade being shaped in such a way that the sharp-edged portion LT moves, for a short axial travel of the elongate body C, from a substantially axial orientation to a substantially transverse orientation, characterised in that the terminal face of the elongate body which comprises a slot F for the passage of the blade is formed in such a way that it has a ball-centring spherical cavity CS. IMAGE