A description of rivets, their use, and materials with a list of manufacturers
You will learn:
A rivet is a permanent mechanical fastener that is used to join materials. Their wide use is due to their ability to withstand vibrations and tension without loosening, factors that make them a far better fastener than screws or bolts. Rivets consist of a head at one end and a cylindrical shape at the other end referred to as the shaft or tail. The tapered end or tail, has the appearance of a metal pin and is the portion of a rivet that secures joints. The shaft can be hollow and contain a mandrel or be solid. It is the portion of a rivet that is deformed to secure the connection of materials.
The installation of a rivet begins with the drilling or punching of a hole through the surface of the materials to be joined. The rivet is inserted into the holes and upset or bucked by force using a hammer or rivet gun. As the force is applied, the cylindrical tail expands around one and one half times the size of the diameter of the shaft. The process of deformation smashes the shaft and flattens it into a shape that tightly connects the end of a rivet, the shaft, and the head.
The final shape of a rivet includes its original head referred to as the factory head and the deformed shaft end that is called the buck tail. The factory head and buck tail are designed to support tension at either end and prevent the rivet from detaching from the drilled hole. They firmly hold the connected materials together. The connection between the parts of a rivet is due to the shaft firmly holding both ends of the rivet to prevent radial movement. Rivets provide a permanent joint that is similar to welding and the use of structural adhesives.
Rivets are a widely used component that are designed to hold products together. They are used in the manufacture of products due to their ability to create strong and permanent joints. The simple process for installing rivets belays the impact they have on the quality of products. Made from a wide variety of materials, rivets are produced in accordance with the types of application for which they are produced. The initial steps in the production of rivets begins with a rod or wire made of steel, aluminum, copper, bronze, or other type of material.
Regardless of the many different types of rivets, all rivets have the same basic structure. They are produced in different shapes to accommodate their varying uses. Most people envision a rivet as a fastener with a head attached to a cylinder-like shape. In addition, the common assumption is that all rivets are made of steel. Although this concept is true, the wide assortment of rivets is made from varied materials that are selected to fit a specific application. The basic parts of a rivet are its head, body and shank, and its tail.
The first step in the manufacturing process for making rivets is to take round wire or rods and cut them to the desired length. The wire has to be cut long enough to pass through the hole drilled in the materials. This aspect of the process is one of the factors that partially differentiates the types of rivets with some types having longer shafts than others. In addition, the length of the rod has to be long enough to fit into the die.
The process for manufacturing rivets happens rather quickly. Initially the wire or rods are fed into the rivet making machine. Once the rod or wire is cut to the desired length, it immediately moves into a die that has the shape of the head of the rivet. As with all forms of dies used in the manufacturing of metal products, dies for the heads of rivets are made of hardened steel or tungsten, metals that have the durability to cold form rivets. The two types of dies used to manufacture rivets are upset and pull.
In most cases, to achieve the correct rivet body, the wire or rod will receive multiple punches to create a solid rivet body. Although there are multiple applications of the die, the process happens rapidly making it possible to produce 300 rivets per minute.
To remove any form of chemicals and other residue from the rivets, they are placed in a part cleaning machine that tumbles them. During the tumbling cleaning process, the tumbler contains an abrasive media that cleans the rivets as they tumble. The rotary motion creates a sliding cascading action that gently grinds and polishes the surface of the completed rivets. Rotary tumblers are ideal for removing excess material and leftover debris from the cutting, punching, and shaping processes.
After the forming of the head, a rivet is heat treated to change its properties, such as increasing a rivet's strength and hardness. The type of heat treatment is chosen in regard to the material from which the rivet is made, since different materials react differently. The intense heat of the heat treatment anneals the metal freeing it from internal stress. After heat treatment, rivets are coated or plated to protect them from wear and corrosion.
Heat treatment affects the properties of rivets and is chosen to match the material being treated. In most cases, the goal is to enhance the durability of a rivet through heat treatment, which improves the quality of a rivet.
The manufacturing process for the production of rivets is rather simple and varies according to the type of rivets being produced. As with all forms of manufacturing, the effectiveness of the process is dependent on precision, accuracy, and attention to details, regardless of the nature of the process.
The list of materials used to produce rivets vary between plastics and steel, which are chosen in accordance with the application for which a rivet is being used. Plastics, such as nylon, are used when there is concern for the weight of a product while steel is used for its strength, durability, and longevity.
The factors for choosing a material include:
The list of rivets is long and includes a wide assortment of shapes, metals, designs, and configurations in order to meet the demands of modern industrial assemblies. Rivets are a necessity for products due to their dependability and size. They are capable of firmly securing multiple surfaces without shifting, loosening, or failing. The different types of rivets used in an assembly are chosen based on the requirements of a design and the properties of the rivets.
Solid rivets, or round rivets, are the most common and widely used rivet. They are made of a single piece of wire or rod and have the simplest structure. As with all rivets, solid rivets consist of a head and cylinder or shaft. During installation, the headless portion of the rivet gets deformed using a rivet gun or hammer. Solid rivets can have round universal heads or 100 degrees countersunk heads. The wide use of solid rivets is due to their dependability, strength, and safety. They are an essential part of structural applications, such as vehicles and aircraft.
Of the many types of rivets, solid rivets are the oldest and most dependable. Their solid structure makes them strong and durable for critical applications. Aside from their use in vehicles and aircraft, solid rivets are used to produce electronics, machinery, and ship building.
Blind rivets, also known as pop rivets, are tubular fasteners with a mandrel that is pushed through during installation. They are used in situations where there is limited access to one side of a joint. When the mandrel is pulled through the hollow tube of a blind rivet, it expands to form a tight secure connection. Once the mandrel is fully extended, it breaks off.
Three common types of blind rivets are:
Tubular rivets have a head, shank, and partially hollow tube. They are available in a wide range of configurations. All types consist of a head on one end and a tube on the opposite end. Tubular rivets resemble solid rivets with the hollow end replacing the solid end of solid rivets. They are made of ductile materials and low strength metals in order to make connections. Although there are many forms of tubular rivets, the three best known forms are compression, full, and semi, which are differentiated by the structure of their tubes.
Self-piercing rivets, also known as bifurcated rivets, make a hole using a chamfered poke or bevel drill. They pierce the top layer of a material, half piercing the lower layer. The upsetting die used to make self-piercing rivets is designed to make the tail spread and interlock with the base or bottom sheet of the materials to create a self-connecting button. Self-piercing rivets are used for high stress applications and are able to hold dissimilar materials together that are impossible to weld.
During installation, the legs of a self-piercing rivet fold back to hold the joined materials. They are commonly used to produce leather goods, clothing, and carrying cases. Self-piercing rivets require a special tool to be installed.
Split rivets are similar to self-piercing rivets and are used to join pieces of wood, plastic, and leather. They are pre-split along their shaft to form two legs. During installation, as the legs are driven into a material, the legs fold back to hold the joined materials. The legs of a split rivet are made of materials that easily bend or crimp outward. In order to pierce materials, the legs have sharp ends or tips, which enables them to pierce materials.
The nature of split rivets makes them inappropriate for highly critical or extreme applications. This factor is also due to the lightweight of the material used to produce split rivets. Commonly used with softer materials, split rivets are ideal for making flexible joints.
Flush rivets are a form of countersunk rivet and are used on products and surfaces that require a pleasant appearance and the elimination of aerodynamic drag. As the name of flush rivets implies, flush rivets are known for being able to sit flush with a surface to create a smooth even surface. Due to the design of flush rivets, they are often used on the exterior of metal sheets or panels. Their elimination of aerodynamic drag makes them ideal for use on aircraft. The down side of flush rivets is the amount of labor it takes to install them, which limits their use.
The process of flush riveting is a way of connecting materials using rivets whose heads do not protrude above the surface of the joined materials. The four methods to install flush rivets are countersinking, double dimple, pre-dimple, and a combination of two of the methods. The choice of installation method is in regard to the thicknesses of the materials being joined.
Drive rivets, also known as hammer rivets, are like blind rivets in that they have a mandrel in the center of their shaft or shank. Unlike blind rivets, drive rivets require a special tool to draw the mandrel through the rivet. Drive rivets are shorter than other rivets, which makes them easier to fasten. Their mandrel is a short small pin that protrudes from the head of the rivet. When the pin is driven flush with the head, it expands the rivet and secures it. Drive rivets are adaptable to any material and create a high strength permanent bond.
The use of drive rivets is ideal for applications that do not require a puncturing of the whole block, panel, or metal sheet. They are used to hold panels in place or fit nameplates into binding holes. Drive rivets are commonly used when a strong joint is required, but access to one side of the joint is restricted. Regardless of their durable shape and strength of materials, the clamping force of drive rivets is not as great as that of other types of rivets.
Cherry rivets are used with high vibration applications and can be replacements for solid rivets. A specialized use of cherry rivets is with composite materials that may crack when having a rivet installed. Cherry rivets are blind rivets and are used in applications that require strength and stability.
CherryMAX rivets, known as bulbed fasteners, have a built-in mechanical locking washer that makes it possible to install them using a rivet gun. They are referred to as bulbed rivets due to their large blind side bearing surface that develops during installation. Cherry lock rivets require the use of a special tool to pull the head to seat the locking collar of the rivet.
The term cherry rivet is synonymous with the aerospace industry where they are widely used and for which they were first developed. In 1936, Douglas aircraft was experiencing difficulties with its assembly operations because of problems with solid rivets. Carl Cherry developed the cherry rivet that did not require such intensive labor to install.
Threaded rivets, known as rivet nut or nutsert, are blind rivets with a hollow threaded body that houses mating fasteners that prevent the threaded body from coming in direct contact with materials to be joined. The design enables the rivet to tightly grip the material. The collapsible body of a threaded rivet secures the rivet in place and gives it a blind appearance.
The main components of a threaded rivet are its nut, nut tool, mating material, attaching component, and a bolt or screw. The installation of a threaded rivet involves drilling a hole into which the rivet will be placed. As the rivet nut is screwed into the rivet, a bulge or swage is formed joining the materials.
The types of threaded rivets include sealed head, closed or open ended, wedge head, heavy duty flanged, thin or thick walled, hex body, and several others with each type having a unique structure but performing the same function.
There is an endless number of rivets being used by manufacturers to secure materials with new ones being introduced for modern applications. It is nearly impossible to describe all of the different types and kinds of rivets. The sampling provided here are some of the more commonly used types of rivets. The chart below includes other rivets that are common to industrial processes.
| Types of Rivets and Their Uses | ||
|---|---|---|
| Types of Rivet | Characteristics | Applications |
| Snap Head Rivet | Provides solid joints with a head length of 0.7 inches and a shank diameter of 1.6 inches. | Used in industries that require high strength. |
| Friction Lock Rivets | Multipiece rivets with a stem and sleeve. | Aircraft manufacturing, automotive industry, rail and transport engineering. |
| Mushroom Head Rivets | Mushroom like head and a lower profile than regular rivets. Used to lock parts. | Joins materials with different thicknesses. |
| Pan Head Rivets | Has a unique shape with a cylindrical head that slopes downwards from the top. | Heavy duty structural construction projects due to their extraordinary Igrip and strength. |
The types of materials used to produce rivets are as varied as the many types of rivets with some rivets being identified by the material from which they are made. As may be presumed, steel is the central material in the manufacturing of rivets due to its strength, durability, and longevity. Rivets are also made from materials based on the application for which they are made.
Steel is one of the most used metals in the manufacture of rivets. Although many products are made from steel, as with other metals, steel is made up of different alloys that have unique characteristics and properties. Of steel alloys, low carbon steel is the most used for the manufacture of rivets due to its flexibility and adaptability compared to high carbon steel. The choice of either type of steel for making rivets is due to steel’s high tensile strength, hardness, durability, and wear resistance.
Although low carbon steel is weaker than high carbon steel, it still performs well in a variety of applications. The weakness of low carbon steel is due to its low carbon content. Regardless of this factor, it still has sufficient tensile strength to perform well. Both high and low carbon steel rivets are used as structural rivets for aircraft, vehicles, and rail transportation. The characteristics of low carbon steel has made it an important fastener for construction projects and the manufacture of furniture.
Stainless steel is a type of steel that is a combination of iron, chromium, and small amounts of nickel or molybdenum. Like steel, most of stainless steel is iron, which, by itself, does not have the strength of either stainless steel or steel, due to its vulnerability to rust and corrosion. The unique mixture of alloys that produce stainless steel make it resistant to rust and corrosion, which makes it an ideal metal for producing rivets.
Aside from stainless steel’s resistance to deterioration, it is a significantly strong, hard metal with an excellent strength to weight advantage. In addition, the durability of stainless steel extends beyond its resistance factors and includes impact resistance, which is important for rivets.
Although aluminum does not have the strength of steels, it has several properties that make it applicable for the manufacture of rivets. Like stainless steel, aluminum is resistant to rust and corrosion with some having strength that is comparable to certain steels. In addition, aluminum has a naturally formed oxide layer that further protects the metal. Unlike steels, aluminum is strong and lightweight, a factor that is important for modern day products. It is sufficiently malleable to be produced in complex configurations.
Pure aluminum is a pliable, soft metal that has very low structural strength. Various alloys are added to pure aluminum to create the different grades of aluminum. The type of aluminum used for rivets contains magnesium, which makes pure aluminum durable and strong but still resistant to rust and corrosion. The main use of aluminum rivets is in the construction of aircraft, where the rivets are countersunk rivets to eliminate aerodynamic drag.
As with aluminum and stainless steel, copper is resistant to corrosion. Like aluminum, copper, by itself, is a soft metal that is not very strong. Most grades of copper used to produce rivets have alloys added to enhance the strength of copper. The most outstanding characteristic of copper is its conductivity, which is one of the reasons that it is used to produce electrical appliances. Copper rivets have characteristics that have made them ideal for different applications.
Regardless of its malleability, copper is very strong with a higher tensile and shear strength than most other rivets. Its resistance to corrosion has made it useful for applications that are exposed to harsh environments. A property of copper that is seldom found in other rivets is its pleasing decorative appearance, which makes it popular for the manufacture of decorative items.
Brass, a malleable alloy, is made from copper and zinc, a factor that gives the metal its distinct and unique color. It is a flexible metal with low friction and excellent strength. Brass is ideal for producing rivets due to its inability to generate sparks, which is the reason that brass rivets are used with gas appliances. Due to brass’ copper content, it is resistant to corrosion, has high thermal strength, and electrical conductivity. As with copper, brass is also valued for its decorative and pleasing appearance.
Rivets made of brass have high strength and are used to produce marine equipment and for adding architectural highlights. The positive appearance of brass rivets has led to their wide use in the clothing industry in the manufacture of jeans and boots.
When people discuss rivets, they mainly focus on metal rivets, which are the most common. Aside from the many varieties of metal rivets, there are other materials, especially plastics, that are used to produce rivets. Nylon is widely used as rivet material due to its strength and durability. A property of nylon that differentiates it from other forms of rivets is its insulating property, which makes it a popular method for concealing wiring. Unlike other types of rivets, the installation of nylon rivets does not require the use of heavy tools. Nylon rivets can be installed by being inserted into a drilled hole and pressed with the fingers to expand the legs of the rivet. This particular factor is not true for all nylon rivets, with some types requiring the use of heavy tools.
As with metal rivets, plastic or nylon rivets come in a wide assortment of sizes and configurations. Due to the nature of nylon, the appearance of nylon rivets is different from metal rivets. Nylon snap rivets have separate heads that are snapped together and are available as mini rivets. Ratchet nylon rivets have two identical parts that are connected to join materials. The unique nature of nylon rivets goes on and on with each type able to meet the specific needs of an application.
As part of the selection process for rivets, there are metal rivets that can be used with certain metals and ones that should not be used with some types of metal.
| Guide for Metal Rivets Joining Metal Materials | ||||||
|---|---|---|---|---|---|---|
| Rivet Metal | Metals Being Joined | |||||
| Aluminium | Al/Zn Coated Steels | Zinc Coated Steels | Stainless Steel | Copper | Brass | |
| Aluminium | Yes | Yes | – | No | No | No |
| Zinc Plated Steel | No | Yes | Yes | No | No | No |
| Stainless Steel | – | – | – | Yes | Yes | Yes |
| Copper Nickel | No | No | No | Yes | Yes | Yes |
| Copper | No | No | No | Yes | Yes | Yes |
Understanding fasteners is essential in determining the proper fastener for an application. Bolts, rivets, and screws have been used for centuries to join different types of materials. Although these three are a sufficient and strong method, the choice of the correct method is essential for making a strong connection. In addition, there is a vast difference between bolts and screws and rivets.
The most obvious factor that differentiates rivets from screws and bolts are their threads. Rivets do not have threads and make connections through the use of force and pressure.
The variation between bolts and screws and rivets regarding installation is in regard to the amount of force required. Most rivets, regardless of type, require a certain amount of force to create a strong connection. Bolts and screws are installed using a rotational motion to smoothly connect surfaces.
The wide use of rivets to join materials is due to their exceptional shear strength. This aspect of their properties enables them to be installed at all angles without failure.
Rivets are permanent and cannot be adjusted or changed once installed. They form a tight bond that is impossible to change without damaging materials and surfaces.
There are several advantages to using rivets to connect materials. Fasteners are a ubiquitous aspect of product production. Cars, trains, planes, and computers require the use of rivets to create solid tight joints. Rivets are normally chosen for joining materials due to the characteristics of the materials to be connected.
The installation of rivets is less labor intensive since they can be quickly installed using a variety of tools. They are a high efficiency production fastener that is inexpensive and high quality.
Most rivets do not add to the bulk weight of the products in which they are used, which is essential in industries where weight is a significant factor. Their lightweight leads to fuel efficiency and lowering the weight of structures.
Rivets provide permanent connections that are not subject to change and are unaffected by vibrations, impact, or the environment. Once installed, rivets hold materials together without loosening, a factor that is beneficial for structures that are subjected to movement and dynamic loads.
Rivets are quickly and efficiently installed from one side of an assembly, a factor that is important when the back side of a product is inaccessible. The rapidity of installation allows for quick assemblies and lower labor costs.
The wide array of rivets makes it possible to join materials of any thickness. In addition, rivets are rugged enough to join thick resistant materials but gentle enough for delicate thin materials. This particular factor is why rivets are used to manufacture purses and shoes as well as airplanes and trains.
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