| 摘要 |
To provide a fastener having a high anti-loosening effect. [Means to achieve the object] A fastener has a thread structure including an upper portion of the crest and a bottom portion at the groove. The upper portion has a load flank surface inclined from the standard load flank surface toward the fastener seat while the bottom has an undercut on at least one of the groove side lower than the extension of the corresponding flank surface. |
