Patent ID: 6568492
Filing Date: 2003-05-27
Classification: E21B

Abstract:
A drag-type casing mill/drill bit for down hole milling of a casing window and drilling of a bore hole in an earth formation, comprising:a bit body adapted to be rotated in a defined direction, the bit body having an operating end face; a plurality of radially extending blades as a part of the operating end face of the bit body, the blades comprising pockets formed therein; a plurality of primary cutting elements, each element having a cutting face and mounted in a pocket in one of the plurality of blades; and a plurality of secondary ridge structures extending from each of the plurality of blades, each of the secondary ridge structures positioned radially in proximity to at least another one of secondary ridge structures and interspersed with at least one of the plurality of primary cutting elements in a cooperative pattern such that as the bit body rotates at least one of the secondary ridge structures contact the casing or the earth formation thereby limiting the exposure of the cutting face of the primary cutting elements radially positioned from a secondary ridge structure and allowing substantially stable casing milling and earth formation drilling.