| 摘要 |
A drilling bit comprising a drill body formed from a base portion and a crown portion having a plurality of cutting elements; the base and crown portions are interengaged by a connection portion. An external opening in the crown portion communicates with a core-receiving section in the connecting portion. A core milling assembly, comprising a pair of rotatable, frustum-shaped rotary members, is supported in the connecting section. Each rotary member carries a plurality of cutting elements. During drilling, a core is received in the core-receiving section, where it is milled by the rotation of the rotary members.
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