| 摘要 |
PROBLEM TO BE SOLVED: To increase strength of a crest of a thread in a rolled internal thread and a rolled external thread and to prevent a crack so as to increase strength of the threads as a whole. SOLUTION: In the rolled internal thread 1, the crest 4 of the thread 2 is formed so as to have a fixed width in the thread axis direction, while thread axial both ends of the crest 4 and flanks 3a and 3b are connected to each other smoothly via projecting round parts 5. In this way, the crest 4 is prevented from a crack in connection with a counterpart side external thread, and consequently, conventional problems such as reduction in axial force due to a bite of a cracked piece in a thread meshing part and difficulties due to seizure in detaching work can be solved.
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