| 摘要 |
A drill bit includes at least two different sets of cutting elements, each being the primary cutting set corresponding to a different formation. Upon encountering a significant change in formation characteristics, the first set of cutting elements may be sacrific ed so that the second set of cutting elements becomes exposed, preventing the need to replace the drill b it immediately. The sets of cutting elements differ from one another, with each adapted to cut a different formation. The differences may include material toughness (impact resistance), bevel size, abrasion resistance, or backrake angle. Additional sets of cutting elements may be added to correspo nd to other formations or to otherwise improve performance.
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