| 摘要 |
<p>A screw head is provided with ribs (26) on some of the driver engageable surfaces. The rib (26) is slanted outwardly from the screw axis by a small angle A between 1° and 10°. A punch (150) for making a screw head with ribs (26) on some of the driver surfaces includes a slanted groove (168) for providing a rib (26) which is slanted from the screw axis by a small angle A between 1° and 10°.</p> |
