| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of loosening and return during fitting-in by a method wherein a half angle of a thread angle is set to an angle lower than 30 deg. and a pitch between adjoining threads is set to a value lower than an ordinary pitch. SOLUTION: A male screw 3 has a thread angle reduced to a value lower than 60 deg. and symmetrical about a line orthogonal to an axis and lower than 30 deg. by a fine angleαand a thread pitch is lightly lower than the pitch P of a female screw 4 by a fine amount B. A female screw 4 has a thread angle of 60 deg. and 30 deg. symmetrical about a line orthogonal to an axis and a thread pitch is formed at P. When a male screw 2 s fitted in the female screw 4 and slightly fastened, the flank surface 5 on the advance side of the male screw 3 is brought into contact with the flank surface 6 on the advance side of the female screw 4 and the flank surface 7 on the opposite advance side of the other thread of the male screw 3 is brought into pressure contact with the flank surface 8 on the opposite advance side of the other screw of the female screw 4. Thus, since the number of the flank surfaces to be brought into pressure contact is increased, a load on the thread is dispersed and loosening and return are prevented from occurring between the male screw 3 and the female screw 4.
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