| 摘要 |
At least one movable stabilizing member (29) is biased from a first retracted position to a second extended operating position. The body member (1) further comprises at least one fixed stabilizing surface (12) positioned in axially spaced relationship to the at least one movable stabilizing member (29). The movable stabilizing member comprises outer contact faces (36) adapted to engage the walls of a bore hole when in an operating position, and an inner slide surface (44) adapted slidingly engage a corresponding slide surface (45) formed in the body member (1). The method comprises the steps of providing a rotary drill bit (110) having a plurality of wear ridges (39) on the bit face along with a plurality of cutting elements (18) extending outwardly from the bit face to a greater extent than the plurality of cutting elements (18). The drill bit (110) is rotated along with the drill string (62) to initiate a drilling operation or in an existing full gauge hole to form a pilot hole. Upon rotation of the drill bit (110), the plurality of wear ridges will allow rotation of the drill bit and drill string for a period of time before engagement of the plurality of cutting elements.
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