| 摘要 |
Wear sensors 20, 22 are provided on a drill bit or other rotary cutting tool which is for operation in a subterranean borehole and has a plurality of separate cutters 40 protruding from a support structure towards the material to be cut by the tool. The electrically operated sensing means 20, 22 are located at or coupled to a sensing point within a protrusion 28 from the support structure. This sensing point is located such that attrition of at least one cutter 22 to a partially worn state brings the protrusion into abrasive contact with the material 26 being cut and attrition of the protrusion then exposes the sensing point to the material 26 which is being cut by the tool and thereby brings about a detectable change, which may include damage to the sensor 22 at the sensing point, indicative of wear. Also claimed is a rotary cutting tool having a number of sensors fitted at different locations on the tool and monitoring the sensors to observe the pattern of measurements by the sensors. |
