From the miniature electronics to heavy-duty industrial systems, nearly every piece of hardware depends on mechanical fasteners to function effectively. This article offers an in-depth exploration of fasteners and their wide-ranging applications. Ready to take a closer look? Join us as we uncover:
What is a fastener?
Different types of fasteners and their uses
Materials used for making fasteners
How to choose the right fastener for your project
What Is a Fastener?
A fastener is a hardware device used to mechanically join or affixes two or more objects together. It encompasses a broad category of tools—screws, nuts, bolts, washers, rivets, anchors and nails are the varied forms.
Most fasteners can be easily disassembled and reassembled without damaging the components, like screws and bolts. They form a non-permanent joint, but this does not mean the joint is weak; in fact, when properly installed, they can withstand a great degree of stress.
In addition, there are fasteners like welded joints and rivets, which create a permanent bond that cannot be easily disassembled. Depending on the application, fasteners come in various shapes, sizes, and materials, each with its unique function and utility. We will look into these and more in the following passage.
Different Types of Fasteners and Their Uses
As mentioned above, fasteners come in many forms. Each type fulfills unique applications based on its design and functionality. Below is a detailed breakdown of the main types of fasteners, their sub-types, and specific uses.
Type 1: Screws
Screws are highly versatile fasteners, featuring a head and a threaded shank that provide a strong grip and resistance to pull-out forces. Available in various head shapes—such as flat, round, or hex—they can accommodate different tools and aesthetic needs.
Unlike bolts, many screws, such as self-tapping screws, can create their own threads in materials without requiring pre-drilling. They are quick to install using simple tools like screwdrivers or power drills and do not require nuts for fastening. Screws are compatible with a wide range of materials, including wood, plastic, and thin metals. Some of the most common include:
Wood Screws
As the name suggests, wood screws are typically partially threaded and specifically designed for joining pieces of wood. They have a sharp point and coarse threads, allowing them to penetrate wood easily and provide a secure grip.
Machine Screws
These screws have finer threads compared to wood screws, which makes them better suited for hard materials like metal and rigid composites. They feature a consistent shank diameter without tapering at the tip. Typically, machine screws are inserted into pre-drilled, threaded holes or paired with nuts for secure assembly.
Sheet Metal Screws
Sheet metal screws are self-tapping screws specifically designed for thin metal sheets (like sheet metal) and other thin materials. They have a fully threaded shank and a sharp, threaded tip, making it easy to cut threads into thin metal.
Self-Drilling Screws
Self-drilling screws share the fully threaded design of sheet metal screws but come with a drill bit-shaped tip. This distinctive feature allows them to drill directly into hard substrates like steel or aluminum without the need for pre-drilling. They are especially effective for securing thicker metal materials, offering greater efficiency and ease of installation.
Deck Screws
Unlike wood screws, which are primarily used for indoor or protected wood connections, deck screws are wood screws specifically engineered for outdoor applications. They are typically made of stainless steel, galvanized steel, or materials with special anti-corrosion coatings. Deck screws usually have a fully threaded shank, with some designs incorporating double threads or specialized threading to accommodate the expansion, contraction, and stresses caused by temperature and humidity fluctuations.
Hex Lag Screws
Hex lag screws are large wood screws that are designed to be driven with a wrench or socket rather than a screwdriver. With a thick, coarse thread and a hexagonal head, they provide excellent torque and are among the strongest fasteners for metal and wood. These screws require pre-drilled pilot holes due to their size and strength. By their ability to handle heavy loads, they are ideal for structural applications such as frames, decks, and heavy furniture.
Type 2: Bolts
Bolts share a similar structure with screws, featuring external male threads starting at the tips. Unlike screws, bolts are not self-threading and do not cut threads into the material. Instead, they work in conjunction with pre-tapped holes or nuts to create strong mechanical joints. Here are the most popular bolt types:
Hex Head Bolts
Hex head bolts have a hexagonal head; this design makes them easy to tighten or loosen using standard wrenches or power tools, which ensures efficient assembly and disassembly. They are available with machine threads that either extend fully or partially along the bolt's length. Fully threaded bolts excel in applications requiring strong clamping force, while partially threaded bolts, with their smooth shank portion, provide superior shear strength for lateral load-bearing applications.
Carriage Bolts
Carriage bolts have a rounded, convex metal head, followed by a square neck and threaded shaft. The square neck is designed to lock into place within the material, preventing the bolt from rotating during installation and ensuring stability. These bolts are primarily used in wood applications, such as timber framing or furniture assembly.
Eye Bolts
Eye bolts feature a circular loop (or "eye") at one end and a threaded shank at the other. The threaded end is screwed into a surface, while the loop enables easy connection or suspension of objects. These bolts are commonly used in applications that require tension, such as lifting heavy loads or securing ropes and cables to structures.
Socket Head Bolts (Allen Bolts)
These types of fasteners typically have a cylindrical head with a hexagonal recess for the driving tool. An Allen wrench or a hex socket tool can be used for tightening. Compared to traditional bolts, such as hex bolts with external drive heads, socket head bolts have a smaller, more compact head. This design allows for high torque application in tight or confined spaces.
U-Bolts
U-bolts are shaped like a "U" with threads on both ends of the shank. They can wrap around pipes or other cylindrical objects, securing them to a flat surface or structure without causing permanent damage to the pipe or affecting fluid flow.
Double End Bolts
Double end bolts, or stud bolts, are threaded on both ends with an unthreaded shank in the middle. They are used to secure two or more parts from both sides, commonly in applications like flange assemblies or structural connections, where dual-end fastening is required. These bolts can work with a nut at one or both of their ends.
Type 3: Nuts
Nuts are an indispensable partner to bolts. These fasteners have internal threads that pair with bolts of matching thread size and pitch to ensure a secure grip and increased torque. Like bolts and screws, nuts are available in various shapes and sizes. Below are some of the most common types of nuts:
Hex Nuts
As standard six-sided nuts, hex nuts are the most common type, suitable for general-purpose fastening. They are cheap, and you can easily assemble them using a wrench or pliers.
Nylon Lock Nuts
Nylon lock nuts are similar to hex nuts in heir build but feature an additional collar that accommodates a nylon ring or metal insert. This design effectively prevents loosening in high-vibration environments.
Castle Nuts (Slotted Nuts)
Castle nuts feature slots cut into the top of the nut that resemble the battlements of a castle. These slots align with a pre-drilled hole in the bolt or stud, and once the nut is in place, a cotter pin can be inserted through the hole to secure it, preventing loosening.
Flange Nuts
Flange nuts are similar to hex nuts but with a wide flange at the base, which serves as a built-in washer. This design helps to evenly distribute the load over a larger area, reducing the risk of damage to the connected material and enhancing the nut's grip.
Cap Nuts (Acorn Nuts)
Cap nuts, also called dome nuts, have a rounded, closed end that covers the exposed bolt threads. This design protects bolt threads from damage and offer a finished appearance.
Wing Nuts
Wing nuts have two protruding "wings" for easy hand tightening and loosening without the need for tools. Such unique design makes them ideal for applications requiring frequent adjustments, such as temporary fixtures or clamps.
Weld Nuts
Weld nuts are designed to be welded onto a metal surface, creating a permanent threaded attachment point. They often have small projections or ridges (sometimes called “self-aligning projections” or “mounting spikes”) to fasten components in hard-to-reach areas.
Type 4: Washers
Washers are thin, circular pieces of metal or non-metal with central holes. They function as auxiliary fasteners, placed around bolts or screws to provide contact with the nuts or base materials. Washers serve multiple purposes, including distributing load, protecting surfaces, reducing friction, and preventing loosening.
Plain Washers (Flat Washers)
Plain washers have a simple design and are the most commonly used type. They are primarily used to evenly distribute the load of nuts and bolts on components and to prevent surface damage.
Spring Washers
Spring washers, with a slight curve or cut, act like springs by adding tension or preload to maintain tightness, preventing the unintended loosening of fasteners caused by vibrations in the components.
Locking Washers
Unlike spring washers, which rely on elastic force for basic anti-loosening functionality, locking washers primarily prevent loosening through deformation or friction. They are commonly used in dynamic load or high-vibration scenarios, such as industrial machinery and automotive assemblies.
Type 5: Rivets
Rivets are a type of non-threaded, permanent fasteners. They create a strong and durable connection by being inserted into pre-drilled holes in materials and deforming one end to hold the components securely together. The common types of rivets are:
POP Rivets
POP rivets are a type of blind rivets that can be installed from just one side of the material, making them perfect for situations where access to the back is limited. They have a tubular body and a mandrel that, when pulled, causes the rivets to expand and securely hold the materials together. POP rivets are commonly used to join thin materials, such as metal sheets, plastics, and composites, providing a quick and efficient fastening solution.
Drive Rivets
Drive rivets, like POP rivets, can be installed from one side without access to the back of the rivet and are commonly used for fastening thin materials. While POP rivets are designed for high-strength applications, drive rivets are better suited for lighter-duty tasks. They are commonly found in general assembly and light industrial applications, particularly in household and low-stress settings.
Tri-Fold Rivets
Tri-Fold rivets are a variation of blind rivets and are also installed from one side of the material. Their most typical feature is the special mandrel, which causes the rivet body to expand into three distinct “folds” when installed. This provides a larger surface area, offering stronger holding power than standard blind rivets and greater versatility for fastening materials with varying thicknesses.
Large Flange Rivets
The most notable feature of large flange rivets is their large, wide flange, which provides a larger surface area for better load distribution. This helps to prevent damage to softer or more fragile materials, such as thin sheet metals or plastics, during installation.
Semi-Tubular Rivets
Designed with a partial hole at the tip, semi-tubular rivets reduce the force required during installation. While they are not as strong as solid rivets, semi-tubular rivets provide a better shear strength than some other types of blind rivets, offering a balance of strength and ease of installation.
Type 6: Anchors
Anchors are a type of fasteners specifically designed to provide stable fixation in substrates such as concrete, brick, or drywall. Unlike bolts or screws, anchors create secure connections in brittle or hollow substrates. The three most widely used types are:
Expansion Anchors
Expansion anchors are designed for solid base materials like concrete, brick, or stone. They operate by mechanically expanding within a pre-drilled hole when the bolt or screw is tightened, generating friction to securely hold the anchor in place. Requiring no curing time for adhesives, they can be used immediately after installation. Capable of withstanding high tensile and shear loads, expansion anchors are suitable for medium to heavy-duty fastening needs.
Plastic Anchors
Plastic anchors are lightweight fasteners designed for soft or hollow materials like drywall or plaster. They expand as screws are inserted, providing secure, corrosion-resistant connections for light loads, such as picture frames or small fixtures.
Toggle Bolts
Toggle bolts have a similar appearance to traditional bolts but are distinct due to their expanding wing mechanism, which makes them function more like anchors. Their primary function is to provide support within hollow or weak materials by expanding behind the surface and distributing the load across a wider area. As a result, toggle bolts can handle much heavier loads than plastic or expansion anchors. They offer exceptional holding power and vibration resistance, which makes them suitable for securing heavy items such as mirrors, shelves, or TVs to drywall or hollow walls.
Type 7: Nails
Nails are one of the oldest types of fasteners, featuring a simple design with a pointed tip and flat head. Unlike screws, they lack threads and are driven into materials by impact, relying on friction and clamping pressure for hold. They are generally undetachable, and are primarily used with softer materials such as wood, lightweight plastics, or thin metals. Here we have discussed some major types of nails:
Common Nails
Common nails are strong and durable, with a large flat head for easy hammering. They are widely used in structural woodwork and heavy-duty projects requiring reliable fastening.
Box Nails
Box nails are thinner than common nails, reducing the likelihood of splitting wood. They are suited for light framing and woodworking for a clean, finished look.
Finishing Nails
Similar to box nails, finishing nails are used for joining and finishing woodwork. They are often with smaller heads (nearly invisible) for a clean and polished appearance. They are ideal for trim work, cabinetry, and other decorative woodworking tasks.
Roofing Nails
Roofing nails are equipped with a wide, flat head and a rust-resistant coating to endure harsh weather. Their shank may include ringed threads for enhancing grip, which makes them work effectively for securing shingles or metal roofing panels.
Flooring Nails
Flooring nails have a unique design that ensures they stay flush with or below the surface, preventing unevenness. They’re commonly used for securing floorboards tightly in place.
Materials Used for Making Fasteners
Fasteners are manufactured from various materials to meet diverse mechanical, environmental, and aesthetic requirements. Below are the most common materials used and their key applications:
Steel
Steel is the most widely used material for fasteners, accounting for around 90% of production. Its popularity stems from its strength, durability, and affordability. Steel fasteners are available in various grades and can be used in their plain form or with surface treatments such as zinc plating or galvanization.
Carbon Steel
Industries commonly use carbon steel for fasteners, with three standard SAE grades based on strength and applications:
Grade 2 fasteners are made from low-carbon steel, widely used for general hardware applications. They are cost-efficient but less durable, suitable for light-duty tasks.
Grade 5 fasteners are medium-carbon steel, heat-treated to improve strength and durability. These fasteners are commonly used in the automotive industry for mechanical and structural components.
Grade 8 fasteners are high-strength, heat-treated carbon steel designed for heavy-duty applications. They are optimized for high-stress environments such as vehicle suspensions or industrial machinery.
Alloy Steel
Alloy steel fasteners are commonly used in high-load or critical applications, such as aerospace, heavy equipment, and high-temperature environments. However, they require proper design to avoid brittleness, especially under extreme conditions.
Stainless Steel
By mixing high chromium content, stainless steel naturally form a protective oxide layer, which provides outstanding corrosion resistance. This makes stainless steel fasteners become a great choice for harsh environments. Some of the most commonly used grades include:
304 stainless steel fasteners are the most common grade, offering a good balance of corrosion resistance and strength; suitable for general-purpose applications.
Stainless Steel 410 fasteners provide high hardness and wear resistance, and they are well-suited for mechanical components. However, their corrosion resistance is lower compared to other grades.
Stainless Steel 316 fasteners contain added molybdenum, providing superior corrosion resistance, and are often chosen for marine, chemical, and medical applications.
Brass
Brass fasteners are highly corrosion-resistant and have excellent thermal and electrical conductivity. They are commonly used in electrical components, decorative fixtures, and water-exposed applications such as plumbing systems and marine hardware.
Aluminum
Lightweight, corrosion-resistant, and non-magnetic, aluminum fasteners are ideal for applications where weight is a concern, such as in the aerospace and automotive industries. These fasteners can maintain their corrosion resistance even when scratched or damaged, thanks to the self-healing properties of their oxide layer. Manufacturers often combine aluminum with elements like zinc, silicon, magnesium, iron, and copper to enhance strength and functionality.
Titanium
Titanium fasteners are preferred for their superior strength-to-weight ratio and resistance to extreme conditions. Despite their higher cost, they remain a top choice for demanding applications in aerospace, medical, and chemical industries.
Plastic
Although plastic fasteners typically have lower strength compared to metals, they are widely used due to their unique properties, such as electrical and thermal insulation, chemical resistance, and lightweight construction.
How to Choose the Right Fastener for Your Project
To ensure a secure and durable assembly, selecting the right fastener is crucial. Here are the key factors to consider.
Understand the Application Requirements
The fastener type you will finally select always depends on the specific requirements of your application. For heavy-duty uses like construction or heavy machinery, alloy steel bolts are a top choice, while screws or rivets may be sufficient for lighter-duty connections. Environmental conditions are also key—stainless steel or galvanized fasteners resist rust in outdoor settings, while titanium or heat-resistant alloys perform better in high-temperature environments. Don’t forget to factor in vibrations too; in high-vibration areas, a prevailing torque locknut can keep fasteners secure and prevent them from coming loose.
Select the Right Thread
Thread type is a critical factor when choosing the right fastener. Coarse threads (UNC) tighten faster with fewer turns, resist stripping, and work well in materials like wood or softer metals. Conversely, fine threads (UNF) offer better engagement and higher tensile strength, which is beneficial for precision equipment or when a stronger hold is needed.
Evaluate Fastener Materials
The material of a fastener is a decisive factor in ensuring its performance, durability, and suitability for the application. Carbon steel is a popular choice for its strength and cost-effectiveness, while alloy steel offers enhanced strength for high-stress environments, though its brittleness requires careful consideration. If your project involves exposure to moisture or chemicals—like in water treatment facilities—stainless steel fasteners are perfect because of their excellent corrosion resistance. Materials like brass provide corrosion resistance and good electrical conductivity. For applications where weight reduction is critical, you can consider aluminum, titanium or plastic.
In addition to the factors mentioned above, there are many other aspects to consider, such as cost, installation time, and convenience. If you’re still uncertain which fasteners are best suited for your needs, feel free to contact Chiggo! Our professional team is always here to provide expert advice and help you make the best choice.
