| 摘要 |
PROBLEM TO BE SOLVED: To remarkably harden a surface layer in order to provide a drilling tapping screw high in boring properties against a non-fastened item such as a thin metal sheet. SOLUTION: In this drilling tapping screw formed out of a shank 3 having a ridge 5 over the outer circumference, a head integrally formed with the shank 3 at the upper end part of the shank, and of a drill part 4 formed integrally with the shank 3 at the lower end part of the shank, and the surface of the screw is treated with a corrosion preventive coating, no corrosion resistant coating is applied over the surface of the drill part, but let iron as a ground metal be thereby exposed. Therefore, tapping time required by the drilling tapping screw can be shortened, the head part of the screw is less damaged, the yield of the screw is thereby enhanced, and furthermore, retapping the screw for correction is reduced in frequency for thereby enhancing an operating efficiency.
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