| 摘要 |
The wrenching portion of a nut or a bolt head is provided with a configuration which, when viewed in plan, comprises an outer cylinder having a plurality of grooves defined in part by re-entrant concave surfaces and equiangularly spaced about its periphery, the regions of intersection of the grooves with the outer cylinder being planar. The grooves may be altogether part-cylindrical in cross section, or may they have a part-cylindrical bottom surface which merges with two planar inclined side surfaces. |
