A cap nut is also called an acorn nut or dome nut. Hex dome nuts or acorn nuts got their names due to the dome-shaped projection on one side of the nut. These nuts are internally threaded fasteners with dome-shaped heads. Acorn nuts are generally made from steel. Acorn cap nuts serve a decorative purpose by concealment the threaded end of the fastener or acting as a cover for bulging, possibly sharp threads. Cap nuts cover the threaded end of a fastener which means they are especially suitable for when a nut is used in applications where the aesthetics matter. The domed head also acts as a shield from any ends on fasteners that could potentially be dangerous such as sharp bolt threads. The dome shape head of acorn nuts protects bolts and screws from stripping enabling them for reuse after maintenance.
Dome nuts are mostly used to protect objects close to the ends of screws from scratches and structural injuries. These nuts also reduce the effects of physical mishaps on human skin if it somehow forcefully hits the fasteners. The external threads of the screws inserted into these nuts are securely enclosed within the dome. In addition to the protection it offers, these nuts provide the structure with an aesthetically pleasing look. These nuts offer a finished appearance to the threaded end. Cap nuts are threaded like outmoded nuts, which makes the removal simple.
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Cap nuts come in different sizes allowing you to choose and use them with screws of any length. By default, the size of the nut is ‘small’ which means it is used for shorter screws. The small projections on the other side provide the structure with the necessary friction to prevent loosening due to vibrations.