ROLLER-CUTTER CORE DRILL BIT Russian patent published in 1994 - IPC

FIELD: drilling equipment. SUBSTANCE: angles between cutting edges 6 of rock cutting members 3 and 4 and tangent lines to outer and inner circumferences of bit in place of their contact with rock cutting members 3 and 4 are equal to each other. These angles obey relation n×π/2, where n is real number larger than zero but less than two. EFFECT: increased service life in operation in rocks of alternating hardness. 2 cl, 2 dwg