| 摘要 |
PROBLEM TO BE SOLVED: To provide a self-tapping screw capable of obtaining a large fastening force by carving high-accuracy female threads with small driving torque. SOLUTION: The self-tapping screw has a screw shank 2 stretching down from a screw head, where the shank 2 portion stretching just under the screw head is furnished with a plurality of equally high male threads 3, and in continuity from the male threads 3, the forefront portion of the shank 2 is furnished with a plurality of low male threads 4 whose heights decrease gradually toward the end face of the forefront portion, and minute arcuate surfaces 7 are continuously formed in the joints between the upper and lower flanks 5 of each low male thread 4 and the upper and lower bottom surfaces 6, wherein each minute arcuate surface 7 is arranged extending over the joint of at least the lower flank 5 and the lower bottom surface 6 of each end-part equally high male thread 3a continuous to the low male thread 4. COPYRIGHT: (C)2011,JPO&INPIT
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