| 摘要 |
An improved rotary drill bit comprised of two or more elongated generally cylindrical drill members, the lower ends of which form a cutting face. A plurality of vertically spaced rows of rotatable cutting members are positioned around and between the drill members and are journaled thereto whereby as the lowermost row of the rotatable cutting members and the lower ends of the drill members wear away, the next adjacent row of cutting members is exposed.
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