SPAARSKAERANDE BORRKRONA OCH FOERFARANDE FOER BORRNING MED DENSAMMA

摘要

An improved earth drilling bit and method that cuts at least one annular kerf ahead of at least one rolling cutter and provides for rock chip removal and bit cooling thereby increasing drilling rate and bit performance. One embodiment of the invention includes a bit body having a lower end forming an annular kerf cutter for cutting an outer annular kerf, an inner drill member positioned concentrically within the bit body having a lower end forming an annular kerf cutter for cutting an inner annular kerf, and at least one rolling cutter mounted to the bit body and extending from the interior of the outer kerf cutter to the longitudinal axis of the drill bit. Other embodiments include a chipway port defined by the drill bit for channeling rock chips away from beneath the bit; baffles for directing and accelerating drilling fluid flow; cutting edges having connecting webbs providing egress for rock chip and drilling fluid; and slots extending along the bit body for reducing surge and swab pressure.