| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a self-boring screw for wood-based material in which screw-in torque can be reduced stably, pull-out resistance can be enlarged stably and variation in screw-in torque performance and pull-out resistance performance for each screw can be reduced. <P>SOLUTION: A length L<SB POS="POST">l</SB>from the root of a preceding-side flank 6 on a vertical cross section including a screw axial line to a crest 7 of threads 5 is made shorter than a length L<SB POS="POST">f</SB>from the root of a following-side flank 8 on a vertical cross section including the screw axial line to the crest 7 of the threads 5 by 20% or more. Therefore, the area of the preceding-side flank is made smaller than the area of the following-side flank in accordance with a ratio L<SB POS="POST">l</SB>/L<SB POS="POST">f</SB>of the lengths. <P>COPYRIGHT: (C)2013,JPO&INPIT |
