More the direction of the cutting elements for bi - central drilling tool for drilling a casing shoe

摘要

A drill-out bi-centre bit includes first and second axes (30, 34) of rotation separated by a distance D, a first region (56) of radius D centred on one of the axes of rotation, a second region (58) of radius D centred on the other of the axes of rotation, and a third region (60) defined by the overlap between the first and second regions, wherein the cutters provided within the third region are designed to withstand cutting in opposing cutting directions. This may be achieved by providing each cutter with two cutting faces, or by providing two groups of cutters, one group arranged to cut in one direction, the other group being designed to cut upon rotation in the other direction, one of the groups protruding from the bit body of the bit to a greater depth than the other group.