(57) A rotary drill bit for use in drilling or coring deep holes in subsurface formations
comprises a bit body (10) having a shank (11) for connection to a drill string, a
plurality of cutting elements (14) mounted at the surface of the bit body, and a channel
in the bit body for supplying drilling fluid to nozzles (17) in the surface of the
bit body for cooling and/or cleaning the cutting elements. The cutting elements (14)
each comprise a thin hard facing layer (19), defining a front cutting face, bonded
to a less hard backing layer (20), and the cutting element is mounted on a carrier
(22) which is received in a socket (23) in the bit body in such manner that, at least
before any wear of the bit has occurred, the carrier (22) is wholly shrouded by the
material of the bit body, the carrier 22 being formed from material which is less
hard than the backing layer (20) of the cutting element (14).
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