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a. A rotary boring bit consisting of two to four cone-shaped, toothed
rollers that are turned by the rotation of the drill rods. Such bits are
used in hard rock in oil well boring and in other deep holes down to 5,000
m and more. See also: tricone bit;
drag bit. Nelson
b. A type of rock-cutting bit used on diamond and rotary drills. The bit
consists of a shank with toothed, circular, or cone-shaped cutter parts
affixed to the head of the bit in such a manner that the cutters roll as
the bit is rotated. Generally used for drilling 10-cm-size or larger holes
in soft to medium-hard rocks, such as shale and limestone. Usually
noncoring and not diamond set. Also called cone bit. CF:
noncoring bit See also:
rock bit;
roller rock bit. Syn:
roller cone bit;
roller-cutter bit; rolling cutter bit; toothed roller bit. Long
Source:
Dictionary of Mining, Mineral, and Related Terms
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