| 摘要 |
<p>An improved fastener comprises of a threaded shank (11), and a head (12) connected to the threaded shank (11) characterized in that the head (12) having a recess (13) that is formed with a plurality of grooves (16) extend in radial direction from a central point (15) to circumferential edge of fastener head (12) to maximize torque transfer and symmetrically spaced in the circumferential of the head (12), whereby each groove (16) is formed with a pair of vertical ridges curved at both periphery sides of the groove (16) to respective end points which is engageable with a driving tool (14) having corresponding bits having its periphery sides formed with sharp corners which conform to the shape of ridges and end points of the fastener recess (13) enabling an interlocking action during the turning of the fastener and thus preventing the bit from slipping out even during high resistance to penetration of the fastener.</p> |
