| 摘要 |
PROBLEM TO BE SOLVED: To provide a self-tapping screw for a sheet metal capable of forming an excellent female screw in a prepared hole by small threading torque irrespective of whether the sheet metal is thick or thin, and also obtaining a large tightening force and an extraction resistant force. SOLUTION: This self-tapping screw 1 comprises a head 2, a parallel screw 3, a tapered screw 4 convergent toward the tip, and a drill 5 which are formed integrally with each other. The tapered screw 4 comprises convergent tapers on threads 41 and bottoms 42. The threads 41 are formed in roughly continuous threads of a circular shape in cross section at least on 2/3 of or longer than their peripheral lengths. The bottoms 42 are formed in roughly polygonal sections having, at least two projected corners not exceeding heights of the threads 41 on their peripheral surfaces, per turn. COPYRIGHT: (C)2006,JPO&NCIPI
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