| 摘要 |
A drill bit with a bit body having a central bore in communication with a plurality of nozzles for directing drilling fluid; a plurality of cutters defining a cutting face of the bit; and a passageway extending from the central bore toward the cutting face, such that excessive wear of the cutting face opens the passageway to allow the drilling fluid to flow therethrough, thereby reducing a surface pressure of the drilling fluid and indicating excessive wear of the bit. The passageway may extend to adjacent, or within one half inch or three inches of, the cutting face, such that excessive wear opens the passageway to the cutting face. In some cases, the passageway may actually extend through the cutting face with a plug inserted into the passageway at the cutting face to prevent the drilling fluid from exiting the passageway absent wear of the bit. |
