| 摘要 |
PROBLEM TO BE SOLVED: To easily sink a head part of a self-boring screw by threadedly engaging the screw into a backing material and internal/external facing materials such as a soft or hard wooden material, plywood, a cement board, a plaster board, and a siding board without fracturing the screw head and preventing fluffing and protrusion from being formed. SOLUTION: This self-boring screw is provided with an acute tip part, a shaft part having a male screw, a tapered neck part, a cylindrical head part with a cross recess into which a screw driver bit is engaged, and a plurality of serrations which are radially disposed from the shaft part in the opposite end of the tip part towards the bottom of the head, formed into a projecting shape and has triangle cross section of a serration crossing at right angles with a screw shaft in the neck. It is so arranged that the edge of the serration on the tip side is positioned rearward of the edge side of the serration on the head side relative to the screw threading rotation direction and an annular cutting edge projecting toward the screw tip side is formed in the outer circumferential end of the head part so that this self-boring screw is prevented from fluffing and protrusion from being formed, when it is driven into the internal/ external facing and backing materials.
|
