| 摘要 |
An oil well pipe screw joint having a load surface whose load flank angle is negative, wherein at a position where the load surface is bisected in the direction of the height of the male threads, the load flank angle is changed such that the upper load flank angle is smaller than the lower one; and a threading method and an apparatus therefor, wherein, in cutting threads for an oil well pipe screw joint having a load surface whose flank angle on one side is negative by using a chaser having a cutting edge corresponding to the thread shape in question, a plurality of chasers having many kinds of cutting edge shapes successively assigned thereto which are to be used from the start to the end of thread cutting are attached to a single rotary body so that a single thread can be cut by one revolution of the rotary body.
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