| 摘要 |
A percussion-rotary drill includes a shaft (2) and a one-piece, hard material head (3, 3', 3'') having two major cutting bits (4) each having a main cutting edge (5), and two minor cutting bits (6) each having a minor cutting edge (7) axially offset rearwardly along a rotational axis (A) of the drilling head (3, 3', 3'') relative to an adjacent major cutting edge (5), with the two minor cutting bits (6) each having, in its radially outer region on both sides of the minor cutting edge (7), a tangential edge (8) extending at an angle thereto.
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