Abstract: To provide a fastener having a high anti-loosening effect. 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.

Abstract: To provide a fastener having a high anti-loosening effect. 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.

Abstract: A fastening member that exerts a high loosening-inhibition effect is provided. A fastening member 1 has an upper portion 11 on a thread top portion side and a lower portion 12 on a thread root side in at least a part of a thread 10. The upper portion 11 and the lower portion 12 have following constructions. A pressure-side flank surface 13 and a play-side flank surface 14 are formed on the upper portion 11. A pressure-side side surface 15 and a play-side side surface 16 are formed on the lower portion 12. The pressure-side side surface 15 is formed to be continuous from a lower end of the pressure-side flank surface 13.

Abstract: A fastening member that exerts a high loosening-inhibition effect is provided. A fastening member 1 has an upper portion 11 on a thread top portion side and a lower portion 12 on a thread root side in at least a part of a thread 10. The upper portion 11 and the lower portion 12 have following constructions. A pressure-side flank surface 13 and a play-side flank surface 14 are formed on the upper portion 11. A pressure-side side surface 15 and a play-side side surface 16 are formed on the lower portion 12. The pressure-side side surface 15 is formed to be continuous from a lower end of the pressure-side flank surface 13.

Abstract: To provide a fastener having a high anti-loosening effect. 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.