| 摘要 |
A screw has a shank (8) with an oval cross sectional area along its complete length. The shank (8) includes a single spiral oval thread (3) that starts in a pronounced gimlet point (9) at the tip, an unthreaded oval portion of shank (7) and a twin spiral oval high-low thread (5) that finishes under the head (2) and is no more than 10% of the length of the single spiral thread (3). |
