ROTATION DRILL BIT Russian patent published in 1995 - IPC

FIELD: well drilling. SUBSTANCE: drill bit has body with central water course and blades which are two-stage in cross-section. Blade front stage is made leading, and the rear blade stage is lagging. End face of blade front stage is reinforced with wear-resistant inserts installed flush with end face. End face of blade rear stage has rock-cutting inserts whose cutting edges leave behind front stage end face. Value of lagging of rear stage end face behind similar surface of blade front stage increases from center to periphery of bit. End face of blade rear stage may be made in form of parabola inclined relative to end face of blade front stage, or made stepped. Blades form main cuttings discharge recess of bit. Made on blade end faces between steps are additional cutting discharge recesses. EFFECT: higher efficiency. 4 cl, 5 dwg