| 摘要 |
A sealing fastener includes an insert made of metal such as steel and a cap made of a non-ferrous and non-corrosive material such as aluminum. The cap is formed around and is captivated on the upper end portion of the insert by an impact extrusion process. The insert is formed with a head-retaining portion, a flange and a threaded shank. During impact extrusion, the cap is molded over the head-retaining portion and the top of the flange, around the peripheral edge of the flange and under the marginal portion of the underside of the flange. The upper side of the flange is formed with angularly spaced grooves and the outer edge of the flange is formed with scallops to help prevent the cap from turning relative to the insert when the fastener is tightened.
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