BIT FOR HORIZONTAL DIRECTIONAL BORING

摘要

A bit (20) for directional drilling includes a bit body (21) having a frontwardly facing sloped face (24) for steering the bit (20). The sloped face (24) defines a steering plane (P) that defines an acute included angle (X or Y) relative to a lengthwise axis of rotation {R} of the bit (20). A connection (26) is provided at the rear of the bit body (21) of removably mounting the bit (20) to a drill string, and one or more internal passages ( 31 and 32) within the bit body (21) to carry a drilling fluid to a front end of the bit body (21). A first cutting tooth (22) is mounted on the bit body (21) and extends frontwardly from the bit body (21) at a first angle (X) that causes the first tooth (22) to cut along a first circular path as the bit (20) rotates. A second cutting tooth (23) is mounted on the bit body (21) and extends frontwardly from the bit body (21) at a second angle (Y) that causes the second tooth (23) to cut along a second circular path, which has a diameter greater than that of the first path, and wherein a cutting tip (37) at the front end of the second tooth (23) is rearwardly offset from a cutting tip (37) at the front end of the first tooth (22). The second tooth (23) widens the smaller hole started by the first tooth (22). The two teeth (22 and 23) may also be used to drill over a limited angle to steer the bit (20) in rock and the sloped face (24) can be used to push to steer when the bit (20) is in dirt.