| 摘要 |
<p>The screw has a threaded shank. Its head has a conical base with a cylindrical upper section, recessed for polygonal shaped key. Steps are machined around the circumference of the conical base, and these mate with similar steps cut with a milling tool into the upper piece of material, being clamped. The dias. of the steps are arranged to allow a clearance. This arrangement of steps gives reduced friction, increases clamping strength, distributes clamping forces reduces rupture, and gives a locking action.</p> |
