| 摘要 |
<p>A threaded fastener having a groove (13) or projection in a head (2) for engagement of jointing equipment is disclosed. The groove (13) or projection is composed of a center portion (A) and a radial portion (B) extending radially, outward of circumference of the center portion (A). The radial portion (B) includes a straight portion (13a) for receiving torque constantly and a rounded corner (13b) to prevent stress concentration for providing substantial strength against press-molding and applied torque.</p> |
