DRILLING BIT FOR DIAMETER EXPANSION Russian patent published in 2017 - IPC B28D1/14 E21B10/32 

FIELD: mining.

SUBSTANCE: bit inserted for use into the prepared hole drilled in the structure comprises: a cutting blade portion that has a plurality of separate cutting blade portions used to bore sections of the prepared hole; a cutting blade retaining portion that supports a plurality of separate portions of the cutting blade in the radial direction with the possibility of sliding; and a shank portion that supports the cutting blade retaining portion. Plurality of individual portions of the cutting blade are arranged in a circumferential direction and placed on a plurality of steps in the shaft direction. Plurality of individual portions of the cutting blade of the respective steps are set in sliding by the centrifugal force resulting from the rotation, so as to expand radially outwards with the respect to the cutting blade retaining portion. Plurality of individual parts of the cutting blade of the respective steps have different movement pitches in the radial direction.

EFFECT: increased efficiency of diameter expansion by boring.

8 cl, 10 dwg