| 摘要 |
The invention is embodied in a percussion drill bit which comprises a steel body with a working front head portion having a front central zone and plural wing zones radiating from the central zone and being spaced at the outer circumferential edges thereof; first gauge-cutting PCD inserts are secured in the wing zones to extend forwardly at an angle relative to the axis of the bit, and of at least one second core-cutting PCD insert is non-axially secured to extend forwardly from the central zone.
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