| 摘要 |
<p>A screw (10) having a screw-threaded shank (14) and a circular head (12), the head being provided with three radially extending screwdriver tip receiving portions (16; 18; 20) defined between three first, off-central integrally formed projections (16a; 18a; 20a) designed to become shaved-off the screw head by a pre-set shear force applied during tightening of the screw, and three second, integrally formed projections (16c; 18c; 20c) designed to withstand a shear force greater than the said pre-set force applied during slackening of the screw.</p> |
