Riveted joints make use of rivets to make the joints. This is one of the most widely used cold joining processes to fasten sheet metals. A rivet is a short cylindrical non-threaded mechanical device. Because of the presence of rivets, the joint is known as a riveted joint. In this article, we will explore more about riveted joints, their types, and applications.
What are Riveted Joints?
Riveted joints are permanent fastening joints for joining mainly two parts (plates or sheets). A rivet held the parts together with an integral head at the top and a narrow tail at the bottom. The short cylindrical part in between the head and tail is known as the shank. So, the riveted joint can be defined as a permanent joint between two sheet metals using rivets without any application of heat.
What are Rivets?
A rivet is a well-known mechanical fastener having 3 parts (Fig. 1A); Head, Body or Shank, and Tail. Common materials used for producing rivets are Mild Steel, Copper, Brass, Aluminum, etc. The upper-most part known as the head can have various shapes depending on its applications. The bottom part of the Rivet known as the tail is usually tapered. The length of the tail is usually (1/4)D.
Based on the heads used on rivets, they are classified into various types as listed below:
- Snap head or cup head rivets
- Conical head rivets
- Pan head rivets
- Countersunk/Oval countersunk head rivets
- Flathead rivets
- Hollow head rivets.
- Bifurcated head rivet
Snap Head or Cup Head Rivets
Snap head and cup head rivets are two common types of fasteners used in various industries. Snap head rivets have a flat, oval-shaped head that “snaps” into place when the rivet is inserted and tightened. This head design provides a smooth and flush finish on the surface of the material being fastened. Cup head rivets, on the other hand, have a slightly rounded head that resembles a cup. This head design provides a stronger grip on the material being fastened and is often used in applications where a stronger hold is needed.
Conical Head Rivets
Conical head rivets are a popular type of fastener that are commonly used in various industrial and manufacturing applications. These rivets feature a unique conical head design that allows for easy insertion and a secure hold. Unlike other types of rivets, conical head rivets do not require a special tool for installation, making them an economical and efficient option. They are typically made from materials such as steel, aluminum, or brass, and come in a range of sizes and lengths to accommodate different applications.
Pan Head Rivets
Pan head rivets consist of a head that is flat and circular in shape, with a raised center that resembles a shallow dome. The design of the pan head allows it to distribute force evenly across the surface of the material being fastened, which helps to prevent damage and ensure a secure hold. Pan head rivets are typically made from materials such as aluminum, steel, or copper, and are available in a range of sizes and lengths to accommodate different applications.
Countersunk/Oval Countersunk Head Rivets
The countersunk head rivets are designed to sit flush with the surface of the material they are being used on, providing a smooth and seamless finish. On the other hand, oval countersunk head rivets are used when a larger bearing surface is required. These rivets are ideal for applications that require high tensile strength and resistance to shear and vibration. One of the key benefits of countersunk and oval countersunk head rivets is their ability to distribute the load evenly across the joint. This ensures that the joint remains secure, even under heavy loads or extreme conditions.
Flat Head Rivets
Flat head rivets are a type of mechanical fastener that are commonly used in a variety of industrial and manufacturing applications. These rivets are designed to provide a strong and secure connection between two materials by clamping them together using a permanent, non-removable bond. Flat head rivets are typically made from a variety of materials including steel, aluminum, and brass, and can be custom manufactured to meet specific requirements.
Hollow Head Rivets
Hollow head rivets are a type of fastener that is commonly used in various industrial applications. As the name suggests, these rivets have a hollow head, which makes them lighter and more flexible than other types of rivets. They are typically made of aluminum, steel, or copper, and are used for joining two or more materials together. Hollow head rivets are ideal for use in situations where weight is a concern, as they are much lighter than solid rivets. They are also more flexible, which makes them easier to install in tight spaces.
Bifurcated Head Rivet
A bifurcated head rivet is a type of rivet that has two legs on one end and a single head on the other. This type of rivet is commonly used in sheet metal work and in other applications where a strong, permanent joint is required. The bifurcated head rivet is easy to install and provides a secure connection that is resistant to vibration and other forms of stress. One of the key advantages of this type of rivet is that it can be installed from one side of the workpiece, which makes it ideal for use in applications where access is limited.
Applications of Riveted Joints
Riveted joints are a popular choice wherever the application of heat /welding is not easily available or is prohibited. Some of the common applications of riveted joints are:
- Aircraft components and structures
- Boiler Shells
- Railway wagons and coaches
- Bridge parts
- Automotive parts
- Pressure Vessel Components
- Electronic Parts
Types of Riveted Joints
Based on Arrangement of Plates
In general, there are two main types of riveted joints that are widely used. This classification is based on how the plates are used while joining.
- Lap Joint
- Butt Joint
In the lap joint type of riveted joint, the plates are slightly overlapped and joined by inserting the rivet through the coincident hole. The rivets make the connection in the overlapped region.
In the butt joint type, the joining members do not create an overlap, rather they are placed edge to edge. External cover plates (also known as straps) are used while riveting.
Based on type of plates used
Again, depending on how the riveted joints are done while joining (how rivets are arranged in the workpiece while joining), riveted joints are classified into the following types:
- Single Riveted Joints
- Double Riveted Joint
- Chain Riveted Joint
- Zig-zag Riveted Joint
- Diamond Riveted Joint
Single Riveted Joints
Single riveted joint is basically single row riveted joints. The plates are joined by riveting along a line using a single row using either a lap or butt joint.
Double Riveted Joint
As the name suggests, double riveted joints use two rows of rivets for joining each main plate. Both the rows are in the same line of axis. Double riveted joints can be lap or butt joints.
Chain Riveted Joint
In the case of chain riveted joints, the rivets in the adjacent rows are opposite to each other in the same transverse line.
Zig-zag Riveted Joint
When the rivets in the adjacent rows are staggered in such a fashion that every rivet is in the middle of two rivets of the opposite row the joint is known as a zig-zag riveted joint. They have a staggered pitch.
Diamond Riveted Joints
In a diamond riveted joint, the rivets are symmetrically arranged in a diamond pattern about the plate centerline. The number of rivets gradually decreases from the inner to the outer row. Bridge trusses usually use this type of riveting joint. The most common diamond riveted joints are butt joints.
Again, based on the condition of the rivets that are introduced between plates for joining, the riveting process can be of two types:
- Cold Riveting and
- Hot Riveting
While cold riveting is popular for structural joints. In hot riveting, the red hot rivet is introduced between plates to be joined.
- For joining two plates by riveting, holes are punctured/drilled in both plates.
- The diameter of the holes is usually made 1.5mm larger than the nominal rivet diameter.
- In the next step, the hot or cold rivet is introduced between the arranged holes of the plates.
- Riveting can be performed by a riveting machine or by hand.
Assumptions for the Design of Riveted Joint
To simplify the process of the design of riveted joints, certain assumptions are made. Those are:
- Load among all the rivets is assumed to be uniformly distributed.
- The generated stress in the plate is considered to be uniform.
- The shear stress is assumed to be uniform throughout the gross area of rivets.
- Bearing stress between the contact surfaces of the plate and rivet is assumed to be uniform.
- The bending stress in the rivet is neglected.
- The rivet hole is assumed to be completely filled by the rivet.
- The friction force is assumed to be not present between plates.
In conclusion, riveted joints are an essential component of many structures and machines, providing a reliable and long-lasting method of joining metal parts. The different types of riveted joints, including lap joints and butt joints each have their unique advantages and disadvantages, and the choice of joint type will depend on the specific application and load requirements. Understanding the properties and limitations of each type of riveted joint is crucial for designers and engineers who want to ensure the strength, durability, and safety of their structures or machines. With the advancements in welding and other joining methods, riveted joints may not be as commonly used as they once were, but they still have a valuable place in certain applications.