| 摘要 |
<p>The screw has two or three non-circular super-imposed recesses. The depth of each recess is less than 1.2 mm and there is a less than 1?? of draw in each recess. The screw head recess is formed using a punch (10) in a cold-heading process. The punch is formed in a profilating CNC machine, cutting the profiles (12, 14, 16) of the punch to a tolerance of better than ?? 0.025 mm.</p> |
