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