| 摘要 |
A plug is used in welding a female-threaded boss into a hole through a part, the plug being installed in the boss prior to welding (preferably at the plant of the supplier of the bosses, so that they already have the plug installed when they arrive for welding). The plug has a head and a cylindrical portion extending below the head, the cylindrical portion having male threads adapted to be received by the female threads of the boss. The head has a minimum transverse dimension of at least the maximum transverse dimension of an upper surface of the boss so as to completely cover the upper surface. The cylindrical threaded portion of the plug has thread-cutting edges defined therein, configured to re-tap the threads of the boss when an installed plug is rotated in the direction necessary to remove the plug from the boss. The head of the plug has a recess therein, having two portions, namely an upper circular recess, and a lower hexagonal recess, the circular recess being configured to receive a tool to permit the plug to be held in place while the weld is effected, and the hexagonal recess permitting a tool to be inserted once the plug is no longer needed, so that it can be unthreaded from the boss. Optionally, a copper cup washer may be used, the cup washer being configured to fit between the head and the boss, with the cup portion extending upwardly away from the boss, to isolate the head and the plug from the boss, thereby reducing any likelihood of the plug and the boss being accidentally welded together.
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