| 摘要 |
A drill bit has a plurality of cemented carbide buttons embedded in a front end of the drill body. Each button includes a cemented carbide body having a rear mounting portion embedded in the drill body, and a symmetrically shaped crushing end protruding from the drill body. The buttons are oriented at a first acute angle of from about 35° to about 55° relative to the rotational center axis of the drill bit. The crushing end of the button includes at least one annular groove defining axially spaced local maximum points at each side of the groove. An imaginary line touching the maximum points defining a second acute angle relative to the center line of the button. The second angle is smaller than the first acute angle.
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