Rivets are fasteners used to mechanically join a wide variety of materials by expanding the shank or head of a formed pin which passes through a close fitting hole in the material. Rivets are available in a wide range of sizes, designs, and materials, including high-strength structural, tubular, and blind rivets. Some rivet types, particularly heavy structural types, require that the one end of the rivet be peened, or hammered, into shape once the rivet is in place. Lighter rivets such as blind rivets are set, mostly by hand, using a special tool. Rivets are often used as decorative elements and may be made of metals such as brass or copper.
The rivet is one of the oldest types of mechanical fasteners and has been used to fasten wood, leatherm and metal materials since the Bronze Age. Although welding and brazing have largely superseded their use, properly-installed rivets are also one of the strongest and most reliable methods of joining materials. Most rivets work on the principle of “upsetting” or expanding either the shank or the head of a specially-designed pin inserted through a close-fitting hole in the materials to be joined. This forms a tight fit in the hole and the expanded head of the rivet prevents it from pulling out.
Solid, or structural, rivet types consist of a straight, round pin with a half-rounded head on one end. To install these rivets, a hole is drilled through both pieces of material only slightly bigger than the pin shank and the rivet is inserted until the head contacts the material's surface. The blank, or buck-tail, end of the pin is then peened using a hammer or a power tool to expand it to form a second head. This pulls the two pieces of material together tightly and prevents the rivet from pulling out, forming a secure joint. Solid rivet types require that the material can be accessed from both sides for installation.
Blind rivets are more complex in construction, but are easier to install, require access from only one side of the material, and are generally used in lighter applications. They consist of a hollow tubular pin with a head on one end similar to a solid rivet and a special nail that passes through it to protrude beyond its head. The nail has an enlarged ball on its end too big to pass through the pin and features weakening cuts around its girth just above the ball. To install a blind rivet, it is inserted into a hole in the material in the same way as a solid rivet, whereupon a special tool is used to progressively pull the nail up towards the head. This causes the pin to deform and expand to form a head and, when pulled enough, the nail breaks off at the weakening cut leaving the expanded pin in the hole to join the material.
Other rivet types include light-gauge hollow rivets that are typically used to join leather or fabrics, drive rivets, and semi-tubular rivets. Most aircraft skins are attached using large numbers of highly-specialized, friction lock rivets that are countersunk to offer little or no aerodynamic drag during flight. Some specialized rivet types are self-piercing types and do not require the pre-drilling of holes, piercing the material themselves during installation. Others are used purely for decorative purposes and are mostly made from brass or copper.