| 摘要 |
PROBLEM TO BE SOLVED: To provide a fastener capable of obtaining big joint strength by generating no cracking of an end with respect to a joint between MDF (Medium Density Fiber Boards) themselves. SOLUTION: A fastener joining MDF themselves which comprises a guidance portion 1, a thread portion 7, an under thread portion 9, and a head 11 is characterized in that a guidance portion 1 is formed in sawtooth shape, in that the guidance portion 1 has a maximum diameter of circle circumscribed to the guidance portion at a location 4 retreated from a tip 3 of the guidance portion, and in that its maximum circumscribed circle diameter D<SB>1</SB>is formed to be bigger than an outer diameter D<SB>2</SB>of the thread portion 7 by 0.05-0.2 mm. Furthermore, a spiral screw may be formed from the tip 3 of the guidance portion to a base end 5. This makes the joint of MDF themselves obtain the big joint strength without generating the cracking. COPYRIGHT: (C)2008,JPO&INPIT
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