| 摘要 |
Drill pipe for an oil and gas well drill string has a better bench mark system for determining when the tool joints of the drill pipe are no longer satisfactory for sealing. The bench mark is an edge formed in the tool joint in the space between the threads and the make-up shoulder of the tool joint. The edge extends around the circumference of the tool joint for serving as a reference line to measure the distance from the reference line to the make-up shoulder. On the pin type tool joint, the bench mark edge is formed by forming a cylindrical surface in the tapered surface normally located between the threads and make-up shoulder. In the box type tool joint, the bench mark edge is formed by forming a cylindrical surface in the normal tapered surface to create a bench mark shoulder inward from the make-up shoulder.
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