| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw joint for an oil well pipe for reducing variation in shoulder torque. SOLUTION: The screw joint for an oil well pipe comprises a male side pin and a female side box joined by screwing, and includes a screw portion at a location where the pin and the box correspond with each other, and a seal portion and a shoulder portion sequentially connected at the tip end side of the screw portion. At least one taper change point is included in the length area of the screw portion 3 of at least one of the pin 1 side and the box 2 side. The pin screw portion and the box screw portion are preferentially in contact with each other near the center of the screw portion length area by the taper change point. COPYRIGHT: (C)2007,JPO&INPIT
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