| 摘要 |
<p>A drill bit (10) and method of drilling employing a gage definition region (30) on the bit to relatively gradually and incrementally increase the diameter of the borehole being drilled from a diameter that is cut by fixed face cutters (20) or rolling cone cutters on the bit body to a larger diameter. Preferably, the diameter of the gage definition region defined by cutting structures thereon varies along a longitudinal length of the bit, being smallest nearest the leading end of the bit. In a preferred embodiment, the gage definition region includes a plurality of helically arranged cutting elements (26) disposed around the perimeter of the gage definition region. Such a configuration of cutting elements helps to reduce the loading on, and wear of, each individual cutting element. Thus the effective life of the bit is extended by enhancing its ability to drill the borehole to the gage diameter over a longer interval than may be achieved with conventional bit designs. <IMAGE></p> |
