The Different Types of Fasteners and Their Uses
23 July 2020
Fasteners are used to mechanically join two or more objects together, either permanently or non-permanently. There are many different types of fastener, each with their own purpose.
Fasteners can broadly be categorised as either Permanent or Non-Permanent. Permanent Fasteners, such as rivets and nails, are single-use fasteners that are designed to permanently join two materials or parts. Removing the fastener destroys it.
Non-Permanent fasteners, on the other hand are designed to allow for easy removal and re-use. Fasteners such as bolts and screws are commonly used in a number of industries and products as they allow for parts to be dissassmbled and re-assembled if required. Non-Permanent fasteners can be threaded (bolts, screws, etc.) or non-threaded (pins, retaining rings, etc.).
Threaded fasteners are among the most commonly used for assembling components due to the ease in which they can be installed and uninstalled as needed. There are three main types of threaded fastener; Bolts, Screws and Studs.
Bolts have a head on one end (this is usually a hex head) and are threaded on the other. They are generally used in conjunction with a nut (and sometimes a washer) to hold them in place.
Screws are similar to bolts in that they have a head on one end and a thread on the other. They key difference is thet screws are usually used to screw into an internally threaded hole. There are many different types of screws, such as Cap Screws, Machine Screws, and Woodscrews.
Studs are threaded on both ends, and therefore have no head. They are used to join two components with internally threaded holes together.
Fastener threads are standardised to two major standards: ISO (Metric) and ANSI (Unified). Threads can also be right-handed or left-handed, depending on the application. However, the majority of common fasteners are right-hand threaded.
Types of Threaded Fastener
Bolts and Setscrews - Bolts and Setscrews usually feature a hexagonal head with a thread, and can be used either in conjunction with a nut or in a threaded hole. Bolts generally have a shank beneath the head, while Setscrews are threaded all the way up to the head.
Carriage Bolts - Also known as Cup Square Hex Bolts, these have a smooth rounded head with a square beneath. They are used for securing metal to wood.
Eye Bolts - These bolts have a circular ring instead of a traditional head and are used to fix rope or chain to a surface.
U-Bolts - These bolts are used for attaching round objects such as pipes and tubes to a wall or other surface.
Wood Screws - Featuring a smooth shank and tapered point, these screws are used in wood and come in different head shapes such as Philips, Slotted or Pozidriv.
Machine Screws - Machine Screws are used with a nut or tapped hole. Thread Cutting Machine Screws are also available, which feature a thread cutting point.
Self-Tapping Screws - Often referred to as Self-Tappers, these screws are used for in sheet metals. Self-tapping screws tap their own thread.
Socket Screws - These screws feature a smooth shank and an Allen head, and are fastened using an Allen key. Socket screws come with different head shapes, such as Button, Socket Cap and Countersunk.
Grub Screws - Grub screws are a special type fo screw which usually do not have a head. They are used to prevent movement or rotation between two parts.
Nuts are used in conjunction with a bolt to clamo two or more parts together. The most common type of nut is a Hexagonal Nut, but there are several different types of nuts for use in different applications.
Hex Nuts - A plain, hexagonal nut with an internal thread. These are by far the most common type of nut, and are used in numerous industries and applications.
Lock Nuts - These nuts are used when the nut needs to be locked in place without clamping on to another object.
Nylon Insert Nuts - Commonly referred to as a Nyloc nut, these hexagonal shaped nuts have a nylon insert which prevents the nut from coming loose due to vibration.
Shear Nuts - These cone shaped nuts feature a hexagonal gripping point which snaps off when the maximum torque has been reached, leaving just the cone-shaped nut which is difficult to remove.
Wing Nuts - Commonly used in applications where the nut needs to be removed often, Wing Nuts feature two external "wings" which allow for manual turning.
Washers are commonly used between the head of a bolt, screw or nut and the material they are clamping. Their primary function is to increase the bearing area of the head whilst also protecting the material underneath from damage. There are several different types of Washer, each with their own uses.
Flat Washers - These are the most common type of washer and are used to evenly distribute the load of the bolt, screw or nut as the fastener is tightened.
Spring Washers - These locking washers are designed to stop the bolt, screw or nut from vibrating loose.
Cup Washers - Cup Washers form a cup for the head of the fastener to fit in, creating a flush finish with the fastener head. They are used in conjunction with a wood screw.
Repair Washers - Also commonly referred to as Penny Washers or Fender Washers, they feature a small inside diameter hole and are design to create a greater bearing surface and prevent pull-through.
Rivets are a permanent fastener, in that once removed, they cannot be re-used. Rivets are used in a number of industries and applications but are most commonly used to join metal sheets and plates.
Pop Rivets - Consisting of a hat and mandrel, Pop Rivets are used to join two materials together. During installation, the mandrel is forced into the rivet body, forcing the body to expand and grip onto the material(s). Once gripped, the remaining mandrel snaps off.
Large Flange Pop Rivets - Large Flange Pop Rivets are similar to Pop Rivets in their application but feature a much large flange.
Multi-Grip Rivets - These rivets are used when joining materials with differing thicknesses, which would normally require multiple rivet sizes. They are very versatile and cost-effective.