The bits are further classified based on their internal bearings. Each bit has three rotating cones and each one will rotate on its own axis during drilling. While the bits are fixed to the drilling rigs, the rotation of the drill pipe will be in a clockwise direction and the roller cones are rotated in an anti-clockwise direction. Each roller cone rotates on its own axis with the help of the bearing. Again, the bearings are classified mainly into three types: Open bearing bits, Sealed Bearing Bits and Journal Bearing bits.
The cutting structure of the bits varies according to the rock formation. Soft bits will have longer protruding teeth or chisel-shaped buttons, and fewer, more widely arranged teeth. Medium formation bits will have much closer teeth than soft formation bits, and the protrusion of the teeth is reduced. The teeth are very short and closely arranged on hard formation bits. Because of the shorter teeth the penetration of the rock bit during drilling is less than with soft or medium formation bits, but the other bits cannot be used in hard strata.
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