DRILL BIT Russian patent published in 1997 - IPC

FIELD: well drilling. SUBSTANCE: drill bit is assembled of a set of blades different in functional application. The first function is coarse annular drilling out of the well bottom. The second function is calibration well wall so as to keep its diameter. The third function lies in using those as advance extension to provide hydraulic gate. As this takes place hard-alloy tubular cutters the holes of which are open to drill string-borehole annulus. The drill bit has a case with thread to be connected to drill string. Breaking cylindrical front extension has blind slots on outer surface, a flush hole open to the flush hole in drill bit case, and through groove on face open to the blind slots. EFFECT: higher efficiency. 5 cl, 2 dwg