| 摘要 |
A drill bit (1) comprises, on its face, either only curved cutting edges (2) or a combination consisting of at least one straight cutting edge (2') and at least two curved cutting edges (2). The cutting edges (2,2') on the face of the drill bit (1) are arranged such that they start from the axis (4) of the drill bit (1) or end directly adjacent thereto. Three channels (10) start from a blind hole (5) serving to attach the drill bit (1) to an anchor rod of an injection boring anchor, and their openings (11) are not located in the area of the face of the drill bit (1) but are situated in the area of the lateral surface (13) of the same, said lateral surface conically expanding toward the cutting edges (2, 2'). The openings (11) of the channels (10) are placed in the area of concave recesses (12) of the lateral surface (13) of the drill bit (1) in such a manner that they are recessed with regard to the periphery of the face of the drill bit (1). |
