| 摘要 |
An oval screw characterized by making a screw head into the shape of an oval cone which is narrowed upward and the upper part of which has been cut off, by planing the circumference of the top surface of said top-cut oval cone into a circle with a diameter corresponding to the shorter diameter of the original oval top surface, by making the longer diameter part of the original oval top surface into a slow arc slope toward the upper edge of the top-cut oval cone, and by planing off the whole upper edge of the top-cut oval cone. |
