摘要 |
<p>The spacer screw has a sharp tip (10) and has a shank, which is sub-divided into a threaded tip zone (A), a center smooth shank zone (B), and a threaded zone (C) near the head of the screw. The diameter of the zone near the head of the screw is wider than that of the tip zone. The tip zone thread has a thread cutting cam and especially two to six strengthening ribs (6) parallel to the shank (8). The radius of the strengthening ribs is less than that of the cutting cam.</p> |