Drilling device with undercutting

Abstract

The invention is a drilling device for providing a conically shaped cavity in materials primarily used for anchoring systems. The drilling device is comprised of a solid shank for attachment to a drill, a reverse thread section, and a cutting head. The cutting head includes a cutting tip, clean out flutes, extendable cutting blades mounted within an internal chamber of cutting head body, and means for extending the cutting blades. The extendable cutting blades project from the cutting head body radially when the reverse thread section is driven into the internal chamber of the cutting head. The reverse thread section interacts with the means for extending the cutting blades. This may include a pair of cams that are spring biased outwardly. The cams push against the backsides of the extendable cutting blades for driving them from the cutting head body when the drill device is counter rotated. The extendable blades cut a conical cavity at the distal end of a bore hole made by the cutting tip of the cutting head. After the conical cavity is produced, the drilling device is then clockwise rotated to cause the reverse threaded section being at its most distal position to return to its initial position. Biased springs mounted on the outer part of the body push the cutting blades into the body so that the drilling device can be removed from the bore hole.