Bucking bar:Types of rivets
There are a number of types of rivets, designed to meet different cost, accessibility, and strength requirements:
1)Solid rivets
(A typical technical drawing of a universal head solid rivet)
Solid rivets are one of the oldest and most reliable types of fasteners, having been found in archaeological findings dating back to the Bronze Age. Solid rivets consist simply of a shaft and head which are deformed with a hammer or rivet gun. The use of a rivet compression or crimping tool can also be used to deform these type of rivets; this tool is mainly used on rivets closer to the edge since it is limited by its depth of frame. A rivet compression tool does not require two people and is generally the most foolproof way to install solid rivets.Solid rivets are used in applications where reliability and safety count. A typical application for solid rivets can be found within the structural parts of aircraft. Hundreds of thousands of solid rivets are used to assemble the frame of a modern aircraft. Such solid rivets come with rounded (universal) or 100° countersunk heads.
2)Semi-tubular rivets
(A typical technical drawing of a oval head semi-tubular rivet)
Semi-tubular rivets (also known as tubular rivets) are similar to solid rivets, except they have a partial hole (opposite the head) at the tip. The purpose of this hole is to reduce the amount of force needed for application by rolling the tubular portion outward.
Tubular rivets can also be used as pivot points (a joint where movement is preferred) since the swelling of the rivet is only at the tail. The most common machine is the impact riveter and the most common use of semitubular rivets is in lighting, brakes, ladders, binders, HVAC duct work, mechanical products, and electronics. They are offered from 1/16-inch (1.6 mm) to 3/8-inch (9.5 mm) in diameter (other sizes are considered highly special) and can be up to 8 inches (203 mm) long. The finished look of a tubular rivet will have a head on one side, with a rolled over and exposed shallow blind hole on the other. Semi-tubular rivets are the fastest way to rivet in mass production but require a capital investment.
3)Blind rivets
Blind rivets are tubular and are supplied with a mandrel through the center. The rivet assembly is inserted into a hole drilled through the parts to be joined and a specially designed tool used to draw the mandrel into the rivet. This expands the blind end of the rivet and then the mandrel snaps off. (These are also commonly called pop rivets from the sound and feel through the setting tool when the mandrel breaks.) These types of blind rivets have non-locking mandrels and are avoided for critical structural joints because the mandrels may fall out, due to vibration or other reasons, leaving a hollow rivet that will have a significantly lower load carrying capability than solid rivets. Furthermore, because of the mandrel they are more prone to failure from corrosion and vibration. Unlike solid rivets, blind rivets can be inserted and fully installed in a joint from only one side of a part or structure, "blind" to the opposite side.
Internally and externally locked structural blind rivets can be used in aircraft applications, unlike common "pop-rivets", the locked mandrels cannot fall out .Since the mandrel is locked into place, they have the same or greater load carrying capacity as solid rivets and may be used to replace solid rivets on all but it is the most critical stressed aircraft structures.
4)Drive rivet
A drive rivet is a form of blind rivet that has a short mandrel protruding from the head that is driven in with a hammer to flare out the end inserted in the hole. This is commonly used to rivet wood panels into place since the hole does not need to be drilled all the way through the panel, producing an aesthetically pleasing appearance. They can also be used with plastic, metal, and other materials and require no special setting tool other than a hammer and possibly a backing block (steel or some other dense material) placed behind the location of the rivet while hammering it into place. Drive rivets have less clamping force than most other rivets.
5)Flush rivet
A flush rivet is used primarily on external metal surfaces where good appearance and the elimination of unnecessary aerodynamic drag are important. A flush rivet takes advantage of a countersink hole, they are also commonly referred to as countersunk rivets. Countersunk or flush rivets are used extensively on the exterior of aircraft for aerodynamic reasons. Additional post-installation machining may be performed to perfect the airflow.
6)Pop rivet
Pop rivets have limited use on aircraft and are never used for structural repairs. However, they are useful for temporary lining up holes. In addition, some "home built" aircraft utilize Pop rivets. They are available in flat head, countersunk head, and modified flush heads with standard diameters of 1/8, 5/32 and 3/16 inch. Pop rivets are made from soft aluminum alloy, steel, copper, and Monel.
7)Friction-lock rivet
One early form of blind rivet that was the first to be widely used for aircraft construction and repair was the Cherry friction-lock rivet. Originally, Cherry friction-locks were available in two styles, hollow shank pull-through and self-plugging types.
Cherry friction-lock rivets are available in two head styles, universal and 100 degree countersunk. Furthermore, they are usually supplied in three standard diameters, 1/8, 5/32 and 3/16 inch.
A friction-lock rivet cannot replace a solid shank rivet, size for size. When a friction-lock is used to replace a solid shank rivet, it must be at least one size larger in diameter.the reason behind this is that friction-lock rivet loses considerable strength if its center stem falls out due to vibrations or damage.
8)Self-Pierce Rivets
Self-Pierce Riveting (SPR) is a process of joining two or more materials using an engineered rivet. Unlike solid rivets, pop rivets and semi-tubular rivets, self-pierce rivets do not require a drilled or punched hole.
The self-pierce rivet fully pierces the top sheet material(s) but only partially pierces the bottom sheet. As the tail end of the rivet does not break through the bottom sheet it provides a water or gas tight joint. With the influence of the upsetting die, the tail end of the rivet flares and interlocks into the bottom sheet forming a low profile button.
To sum up,rivets need to be harder than the materials being joined, they are heat treated to various levels of hardness depending on the materials ductility and hardness. Rivets come in a range of diameters and lengths depending on the materials being joined, head styles are either flush countersunk or pan heads.
Riveting systems can be manual or automated depending on the application requirements, all systems are very flexible in terms of product design and ease of integration into a manufacturing process.
SPR joins a range of dissimilar materials such as steel, aluminum, plastics, composites and pre-coated or pre-painted materials. Benefits include low energy demands, no heat, fumes, sparks or waste and very repeatable quality.
COLLETED BY HANNS FROM www.buckingbar.com.cn
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