The Ultimate Guide to Fasteners

With so many fasteners available, how do you know which ones to use?

Take screws, for example. They come in different head types, drive types, and materials. We’ve designed this guide to help you understand your options, from plastic knurled head thumb screws to nylon grommet nuts, snap rivets and everything in between.

We recommend that you try before you buy with free samples so that you can ensure they’re exactly what your application requires. You can also download free CADs to help with your design.

Let’s get started.

What you need to know

Already have an idea of what you need? Jump to that section now by clicking on the link below. Otherwise, here are the categories of fasteners you should become familiar with.

Fasteners

Here’s a closer look at the different types of fasteners available, and what your choices are.

Screws

The screw head has two functions:

• Provide the stopping point once the screw is driven into a surface
• House the drive, which is how the screw is turned

Common screw head types and applications include:

The next question is, which type of screw drive do you use? This refers to the kind of tool you use to install or remove the screw. Some examples include slotted, Phillips – or a combination of both – hex and hex socket. Slotted head screws are a great choice if the screws will be turned by hand but should be avoided when using electric screwdrivers. This is because the power forces the screwdriver to slip out and damage your surface.

Hex drives are desirable for tight spaces, while a hex socket requires a hex key, also known as an Allen key, to install. These are for tight tolerances and are less likely to strip the screw than other methods of driving in screws.

If you don’t want your screw heads to show, then use secure screw covers. These are available in different colors to give your application a finished look.

Examples of screws include:

Thumb screws and knobs

Thumb screws have a distinctive look, dictated by their function. Two of the most common types have either a tall, knurled head or a vertical flat head that acts as a sort of key. Both are blunt-nosed with easy-to-grip heads, enabling you to tighten or loosen by hand as needed. This makes them ideal for applications such as safety covers for electronic devices, battery covers and other front panels that require quick and easy access.

Plastic thumb screws with knurled heads often have slotted heads. This allows you to give it a final turn with a flathead screw driver. Wing head thumb screws are another type, which can also perform as thumb screw knobs. They fit any length of standard socket head cap screws with a simple press.

Examples of thumb screws and knobs include:

Bolts

Bolts are often confused with screws, because they do similar jobs. Bolts join two unthreaded components, while screws join threaded components. Usually, the head of bolts is bigger than the shaft. While screws are most often tapered, bolts are not. A bolt needs a nut for tightening, while a screw works on its own.

Like screws, bolts come in a variety of head types, which are designed according to the tool that will engage with it for tightening. Sometimes a bolt is even called a screw. For example, a machine screw can be a type of bolt, but not always. The general rule of thumb is, if it has a hex head, it’s a bolt. If it has a slotted head, such as a Phillips or Flat head, then it’s a screw.

Bolts designed to do specialist jobs are also available. Plastic eye bolts, for example, are used to route and secure wires or cables to another component.

Example of a nylon eye bolt:

Nuts

Nuts, which have threaded holes, work in conjunction with bolts, strengthening the parts they hold together. Usually, most nuts have a hexagonal shape. This is only on the exterior, while the interior is actually cylindrical. The purpose of the hex exterior is to make installation easier. Six sides makes the hex nut easier to grip, which translates to easy installation or removal.

A wing nut has tabs, or wings, on the side, enabling manual turning. This is especially useful if the wing nut has to undergo frequent removal and reinstallation. A thumb nut is also applied manually. Like the wing nut, it’s ideal if the nut needs to be removed often. However, it should never be used as structural support. It works well, for example, on panel and machinery covers.

A cap nut is of a different order all together. It protects exposed bolt threads while also improving safety. Its secondary purpose is to provide a smooth, clean appearance.

Resisting vibrations

Another important aspect is being able to stand up to vibrations, which can loosen the nut, and thus the bolt, causing the joint to fail. In these cases, you should consider a jam nut. This is a lower-profile nut installed below a larger nut. The jam nut should only be tightened between a quarter and a half of the full torque. The other, thicker nut is installed next and fully torqued. This pulls the bolt up through the jam nut. What essentially happens is that both nuts provide opposing forces on the bolt. Joints that fail usually rely on friction, while components such as jam nuts provide tension, which opposes vibrations.

Example of nuts include:

Panel fasteners

Panel fasteners do what the name says: they connect items to panels. They do this on the edge or through holes or slots. However, not all panel fasteners go by that name. Snap rivets are a prime example. Another solution are quarter-turn panel fasteners. These are typically used to secure a panel or cover, yet still enable easy access. Comprising of two pieces, quarter-turn fasteners join a fixed surface with a removable one. The base fits into the fixed panel, and then the slotted screw is inserted through the panel that can be removed, and into the fastener base. A quarter turn of the screw secures – or loosens – the panels. For more solutions that can fasten panels, go to rivets. You can also learn more in our Guide to panel fasteners.

Examples of panel fasteners include:

Rivets

Rivets serve as another type of panel fastener, although their purpose is broader, joining together other items as well.

Push-in rivets, also called push rivets, are particularly popular, as they come in so many different styles. Most simply push into place by hand, hence the name. In some cases, you’ll need a push rivet installation tool, which is easy to use. You can also get removable plastic rivets, which allow you to access the panel and then reuse them.

Snap rivets have male and female parts that pass through the panels to join together and present a finished edge on both sides. Snap rivets are a type of push-in rivet.

Push-in blind rivets are so called because they can be installed even if you can’t access the rear side (“blind” side). An example is a clinch rivet. All you need to install it is a pop rivet installation tool. Another type of blind rivet is the drive rivet. The drive rivet has a short mandrel that protrudes from the head. It’s placed into the hole and a hammer is used to drive the mandrel in, flaring out inside the hole to provide a secure, load-spreading fix. Drive rivets have a specific application, used to secure panels and architectural features to masonry walls.

Solid rivets are the oldest type of rivet, dating back to the Bronze Age. These are another type of push-in rivet. Incredibly strong and durable, solid rivets offer a tamper-proof solution while also resisting vibrations.

You can learn more in our guide: How to choose your plastic rivets.

Examples of rivets include:

Calculating the size rivet you need

A good manufacturer and distributor makes it easy to determine the correct size of rivet you need. For example, Essentra Components tells you the hole diameter range and panel thickness that a rivet will fit. Let’s look at push-in drive rivets, which are easy to install, and mainly used for decorative reasons.

Say you’re fastening two sheets together, and the thickness for each are:

• .061 inch
• .052 inch

The sum total is 0.113 of an inch. Remember that number because we’re going to come back to it.

Figuring the diameter

Figuring the length

Now that we know the diameter needed, we can figure the length.

Now you have your diameter and your length, so you can choose rivets in the correct size.

Threaded rods and studs

Threaded rods are designed to handle a high level of pressure and tension. With that in mind, some people think metal is the only way to go, but that’s not true. Plastic has skyrocketed in popularity as a choice for threaded rods and studs. The reason: plastics’ properties. For example, a nylon threaded rod is extremely strong, easy to cut to size and resists vibrations, abrasions and most chemicals. It’s also non-corrosive, lightweight, electrically insulating, non-magnetic, and has low thermal conductivity. These attributes make it ideal for industries and applications such as:

• Automotive
• Construction
• HVAC
• Electrical
• Marine

What’s the difference between a threaded rod and threaded stud? That depends on who you talk to. In some quarters, they’re one and the same. To others, a threaded stud refers to a shorter length than a threaded rod. A stud also often has a slot in the end for installation.

A dowel pin is another type of fastener, popular with these industries:

• Aerospace
• Automotive
• Equipment manufacturing
• Furniture manufacturing

For example, an acetal dowel pin is inserted into receiving holes, which hold parts of an assembly together through the use of friction. A tight fit keeps the parts firmly together in fixed alignment.

Washers

Washers are used to distribute the load of threaded fasteners by increasing the surface area. They reduce the risk of stress-related damage to the material that the threaded fastener is driving into. Sometimes, washers can give you spacing as well, preventing your fastener from going deeper into the material than you might want.

Using the wrong washers for your application can result in weakening the joint or increasing the threat of loosening a dynamic joint. Just as there are various types of screws, you’ll also find different types of washers.

The flat washer helps reduce surface pressure on softer materials, which in turn decreases the loss of clamp load. The material it’s made of can provide additional properties. For example, nylon flat washers resist chemicals. PVC flat washers resist water absorption.

The shoulder washer is also referred to as an insulation sleeve because it insulates rivets, screws or wires. A nylon shoulder washer, for instance, can be used for connections between incompatible metals. Another nylon shoulder washer is designed to reduce vibrations. A plastic shoulder washer can also be inserted into a housing, giving a rotary application a bearing surface. Another of its capabilities is that it stops heat from flowing through the screw to other parts of the assembly.

Examples of washers include:

High-bond tape

Not every applion requiring fastening should use screws and similar components. Sometimes the best solution is high bond tape. Screws, for example, create stress points. These stress points can rust, become weak and break. High bond tapes eliminate that threat. With an adhesive made of acrylic foam, the tape distributes stress evenly across the joined surface, providing a stronger bond with a seamless appearance

High bond tape also compensates for irregular bonded surfaces. In a perfect world, materials are flat against each other, but we all know this rarely happens. Surface textures, thermal expansion or chemical reactions can impact the bond or create gaps. High bond tape can correct these problems.

If you’re joining metals, corrosion can often result in an accelerated fashion. High bond tape, however, performs as a buffer, preventing bimetallic corrosion. It’s also fast and easy to apply. Screws, for example, can require tools to apply. High bond tape lets you save that time. Simply peel back the liner and apply with pressure.

An example of high bond tape:

Industries

It might help to see the fasteners popular with your industry. Here’s a glance:

Consumer electronics / appliances

Retail / Furniture

Industrial Machinery

Automotive

Here are the most common types of fasteners used in automotive applications.

Healthcare

Here are the most common types of fasteners used when designing and building medical equipment for the healthcare industry.

Materials overview

What your fastener is made of should play a critical role in guiding your choice. Will your fastener be used in or outdoors? What environment will it need to withstand? Are vibrations a factor? Here’s a look at common materials used to make fasteners.

Nylon

Tough, strong and abrasion resistant, Nylon has a very low coefficient to friction. With good thermal and chemical resistance, it also provides resistance to tears, chemicals, and can be formulated to stand up to UV rays. Nylon’s strength means it can be used instead of more expensive and heavier low-strength metals.

You’ll find that nylon 6.6, a variant, is stronger still, and absorbs less moisture than standard nylon. When a high level of torque is required in your fastener, it’s the ideal material. Nylon 6.6 is popular and used to make everything from fasteners to cable ties.

Polyethylene (PE)

Tough and durable, Polyethylene has high impact strength. It also has high ductility, and as a result, provides a degree of flexibility. It’s crush-resistant, protecting applications against damage.

Polypropylene (PP)

Polypropylene is semi-rigid with good fatigue resistance. It also offers superb electrical and chemical resistance (including acids, polyhydric alcohols, neutral salts and basic salts). It has a lower tensile strength than nylon 6/6, but the trade-off is more flexibility. It doesn’t suffer stress-cracking problems and has excellent fatigue resistance, retaining its shape after a lot of torsion. This is a tough material, though it can perform with elasticity.

Polypropylene can also stand up to UV exposure, and depending on the environment, it can be a good choice for outdoor use, especially when you consider that it doesn’t absorb or emit moisture. However, it’s not suited for freezing temperatures, as it can become brittle.

The material has good impact strength, pliability, and is cost-effective. It also offers excellent electrical resistance, so it’s often used in electronics. You’ll find polypropylene used in pharmaceuticals, too, due to its high resistance to many chemicals.

Polyvinyl Chloride (PVC)

With good resistance to oils and low permeability to gases, PVC is inherently self-extinguishing. This makes it an excellent material for wire and cable insulation.

A durable and long-lasting material, PVC also offers flexibility. Unlike some hard plastics, it won’t crack or shred. It also performs as an insulative materials and can withstand high temperatures and chemicals. For these reasons, it’s a popular choice for electrical applications.

Polycarbonate (PC)

Polycarbonate is tough and transparent. It provides high impact strength and high modulus of elasticity. Other benefits include its high heat deflection temperature and very low moisture absorption. It’s a popular material for electrical and electronic applications due to its low frequency and high-voltage insulating properties. Because of its strength and transparency, it’s also ideal for point of sale and displays. 

POM

Polyoxymethylene (POM) is also known as acetal. It’s a highly crystalline thermoplastic favored for its stiffness, hardness, and low creep under stress. It also provides high flexural and tensile strength, has a low coefficient of friction, excellent chemical resistance and outstanding fatigue properties. The flip side is, POM has moderate heat stability and insufficient flame resistance. While it’s the perfect material for many applications, it’s not ideal for those where heat is involved.

PEEK®

PEEK (polyetheretherketone) is a high-performance plastic that maintains stiffness at high temperatures. It has outstanding resistance to harsh chemicals, and excellent mechanical strength and dimensional stability. Another benefit is its resistance to steam and water. All of these reasons make it a favorite of the healthcare industry.

Polysulfone

Polysulfone (PSU) is a transparent material with high-impact resistance. It provides high performance, has good electrical properties and resistance to chemicals. One reason for its popularity is its outstanding hydrolytic stability against hot water and steam sterilization. It performs especially well in high-temperature environments and resists detergents and hydrocarbon oils even in those conditions, under moderate stress levels.

Acetal

Acetal provides high strength and stiffness. Its good dimensional stability makes it an easy material to machine. A semi-crystalline material, acetal has good chemical resistance. It offers a low coefficient of friction and good wear. It has very low moisture absorption while resisting abrasions.

Low-density polyethylene (LDPE)

With high-impact strength, LDPE is rigid, but softer than nylon or HDPE. It performs as a cross between elastomers and thermoplastics. LDPE can withstand the cold, specifically temperatures down to -58˚F (-50˚C) before it becomes brittle. When placed in high temperatures, it quickly becomes soft.

Carbon steel

Carbon steels are iron-carbon alloys containing up to 2.5% carbon. The addition of carbon adds strength to steel, though like any steel, it can still stress and break under pressure. There are different grades of strength in carbon steels. ASI 1022 carbon steel is often used in structural applications with moderate strength, such as bolts and cold formed fasteners, and recessed head screws and low-strength fasteners.

Download free CADs and try before you buy

Free CADs are available for most solutions, which you can download. You can also request free samples to ensure the solutions you’ve chosen are exactly what you need. If you’re not quite sure which product will work best for your application, our experts are always happy to advise you.

Whatever your requirements, you can depend on fast despatch.

Request your free samples or download free CADs now.

Questions?

Email us at sales@essentracomponents.com or speak to one of our experts for further information on the ideal solution for your application 800-847-0486.

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