The Different Types of Nuts and Bolts Explained (With Pictures!)

Simply speaking, nuts and bolts are basically the hardware for fastening two different components together. Let’s start with nuts. Nuts are small pieces of metal, mainly hexagonal in shape, with a hole across the center that is designed for external threads to screw into.

The threading allow the nut to tighten and hold on to the outside threading on a bolt, not boasting, but the weight of the components and sheer friction of the matching threads gives the nut grip.

The fact that it is hexagonal That’s for more comfortable griping with tools, from any vertical or horizontal position, it allows an angle of approach.

There are many different forms of nuts; hex nuts, cap nuts, coupler nuts, wing nuts, turnbuckles, and lock nuts to mention a handful. Each are usually dedicated for a certain job for a given environment; however, as a generalization, nuts are complementary to bolts, and they function in tandem.

Now with all that discussed, and you have an understanding about nuts, let’s talk about bolts. Visualize a metallic rod with a round body and spiral grooves (threads) cut only along some of the length of it. On one end of the bolt forms the head, so you have something to grab onto when twisting it into position.

Bolts can come in a variety of lengths (small, medium, large, and seasonal), but nuts always come standard sizes. In use, bolts are generally designed to resist sheer pulling forces(name called: tensile stess), and should they ever pull or require removal, it picture that the designed forces have exceeded their stress loads on both the nut and bolt.

What is the main difference? Nuts are the small internal threaded pieces that get mated with the externally threaded bolt. Bolts are the longer threaded fasteners they are the part holding everything together. In simple terms: nuts hold bolts, and bolts are the fastening part that held two materials together.

Let’s look further into each of these two parts and how they work in the context of the practical applications of the fastening materials.

What Are Nuts?

Nuts are key mechanical fasteners that work in concert with bolts. Their primary purpose is to securely join multiple components. They most commonly come in metal construction. A nut is a fastener that has a female thread on the inside.

The female internal thread fits onto a male threaded component, in most cases a bolt. The two work together; the person tightening the bolt gets it snug, often relying on a torque rating for the specific bolt application.

Nuts can be found in a completely nonsensical array of shapes and sizes, each to accomplish a very particular type of task. For example, hex nuts are shaped like a traditional hexagon, have 6 sides, and are normally torqued with a wrench.

Wing nuts can be recognized instantly because of their outward projections called wings. Wing nuts allow for easy hand tightening and hand loosening.

Not all nuts are built and designed the same when it comes to security. For example, lock nuts are designed specifically to hold torque and resist loosening caused by vibrating or stressing loads.

Lock nuts often take the design of attempting to keep the physical connection tighter with a clever design, such as a nylon insert, or ridged threads.

Lock nuts are frequently an effective solution for high-stress applications. Examples include bridge construction or any other structural project where fasteners need to stay in place.

For nuts, the base material will almost always be steel. However, brass, aluminum, and plastic are good examples of other materials. Your choice of observing all the factors comes down to the factors you need for your job.

Will the application be subject to strong forces? If so, strength and ductility will be core factors in deciding your base-material choice.

What will be different than the stated option above is whether you will choose corrosion-resistant materials, and/or possibly an alternative to a bolt if your nut is selected. You will want to pay close attention to shape, size, base material, and thread pattern when choosing nuts.

Your bolt style will narrow some of those choices, specifically size and thread pattern. But it does not imply that the nut’s head style and base materials do not require continued thought for the best application.

In conclusion, ensuring the creation of a secure and reliable project starts with some attention to detail at the beginning of the process.

Types of Nuts

Nuts are key mechanical fasteners that work in concert with bolts. Their primary purpose is to securely join multiple components. They most commonly come in metal construction. A nut is a fastener that has a female thread on the inside.

The female internal thread fits onto a male threaded component, in most cases, a bolt. The two work together; the person tightening the bolt gets it snug, often relying on a torque rating for the specific bolt application.

Nuts can be found in a completely nonsensical array of shapes and sizes, each to accomplish a very particular type of task. For example, hex nuts are shaped like a traditional hexagon, have 6 sides, and are normally torqued with a wrench.

Wing nuts can be recognized instantly because of their outward projections called wings. Wing nuts allow for easy hand tightening and hand loosening.

Not all nuts are built and designed the same when it comes to security. For example, lock nuts are designed specifically to hold torque and resist loosening caused by vibrating or stressing loads.

Lock nuts often take the design of attempting to keep the physical connection tighter with a clever design, such as a nylon insert, or ridged threads. Lock nuts are frequently an effective solution for high-stress applications. Examples include bridge construction or any other structural project where fasteners need to stay in place.

For nuts, the base material will almost always be steel. However, brass, aluminum, and plastic are good examples of other materials. Your choice of observing all the factors comes down to the factors you need for your job.

Will the application be subject to strong forces? If so, strength and ductility will be core factors in deciding your base-material choice.

What will be different than the stated option above is whether you will choose corrosion-resistant materials, and/or possibly an alternative to a bolt if your nut is selected.

You will want to pay close attention to shape, size, base-material, and thread-pattern when choosing nuts. Your bolt style will narrow some of those choices; specifically size and thread pattern.

But it does not imply the nut’s head style and base materials do not require continued thought for best application.

In conclusion, ensuring the creation of a secure, and reliable project starts with some attention to detail at the beginning of the process.

1. Cap Nuts

The cap nut, which is typically described as an acorn nut because of its rounded, dome-shaped profile, provides an additional function beyond merely its appearance. The domed shape is intended to cover and protect the external exposed threads and to prevent any inadvertent contact.

2. Castle Nuts

A castellated nut (castle nut, slotted nut) features cuts on the top which allows for the use of a cotter pin as an option to lock the nut while in use to ensure it does not loosen.

Castellated nuts are found in applications with limited torque (e.g., securing a wheel bearing) where a jointed fastening is ideal. The slotted style combined with a cotter pin provides a good fastening method to be easily removed at a later time if needed.

3. Coupling Nuts

A coupling nut is a much longer version of a common nut that is threaded on the inside. Coupling nuts have no external threads, and their hollow body allows the connection of two male threads, such as two pieces of threaded rod.

Coupling nuts have a six-sided outer shape as well, which makes them practical as they can be turned like a nut using a regular wrench.

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4. Flange Serrated Nuts

A Flange Nut is a fastener with a large flange at one end, essentially giving it a built-in washer. However, unlike a washer, a serrated flange is fixed in place and cannot move independently.

One of the main benefits of the serrated flange is that the serrations help evenly distribute the pressure of the nut on the surface of the materials being fastened.

Another benefit of the serrations is that they will create a locking mechanism, helping keep the nut in place and increasing the reliability of the connection.

5. Hex Finish Nuts

The most common type of nut is the hex finish nut. This type of nut is designed to be used with hex cap screws, socket cap screws, or bolts, has six sides, and has internal threads.

When using nuts and bolts, you simply grab a wrench, and tighten them down. Hex finish nuts are often the choice of fastening when you want to ensure reliability in fastening. They are dependable, and easy.

6. Hex Jam Nuts

In general, a jam nut is used where you have to hold it with a nut, but not have to fasten it in relation to another surface.

Hex jam nuts look like hex-finish nuts and have the same shape and same internal threading, but in general, the jam nuts are thinner. The thinner style of the jam nut makes it a good means to use for locking something without taking a whole bunch of space.

7. Heavy Hex Nuts

A heavy hex nut is similar in style to a standard hex nut. It is larger, thicker and heavier than a standard hex nut. A hex nut is a six-sided nut that is threaded on the inside so it can be tightened or loosened with a wrench.

You will often find these nuts are used with hex cap screws or carriage bolts when additional strength or durability is needed.

8. Hex Machine Nuts

A machine nut is a fastener with a hexagonal shape and internal threaded. It is a fastener for machine screws that are less than a quarter inch in diameter.

Machine nuts are typically smaller than hex jam nuts or hex finish nuts and are therefore a good fit for generally lighter duty applications where fit is key.

9. Hex Machine Nuts Small Pattern

A machine nut is a six-sided, internally threaded fastener. Machine nuts are generally more compact and designed as a more lightweight means of fastening than larger hex jam or hex finish nuts and are more specifically used with machine screws smaller than 1/4 inch in diameter. Machine nuts provide a more compact fastening solution in low clearance or narrow conditions.

10. Keps-K Lock Nuts

A keps nut (sometimes called a k-nut, washer nut, or keps-k lock nut) combines a lock washer that spins freely with a nut.

This serves a purpose: the keps nut combines the washer and nut to help speed up the assembly.         

11. Knurled Thumb Nuts

A thumb nut (sometimes called a knurled head nut) has a surface with a knurled or textured surface rather than the normal hexagon or here are ten baby turtles instead of common wrenching surfaces or shapes.

Thumb nuts are prevalent for their aesthetics in decorative instances and for their ability to be hand-adjusted when needed quickly.

12. Nylon Hex Jam Nuts

A low-profile lock nut is designed in a hex shape, has internal tapers and a nylon insert. The nylon insert fulfills an important purpose, it enhances resistance to vibration loosening and resists cross-threading.

The design of the nut assures that it stays in place and does not back off of the fastener when the nut takes on a challenging means of resisting looseness.

13. Nylon Insert Lock Nuts

A nylon insert lock nut will have a hex shape, internal threads, and a nylon insert. The nylon insert serves two purposes: it helps to keep the nut from loosening if there is vibration and prevents cross-threading. This allows the nut to continue holding tightly, and much less likely to back off the bolt when in use.

14. Prevailing Torque Lock Nuts (Stover)

You may know these as stover nuts, but their actual name is prevailing torque lock nuts. One thing you’ll notice right away are the chamfered corners and the slightly conical top.

What really sets them apart is the intentional distortion of the top thread; this allows the nut to resist loosening, even when exposed to a lot of vibration.

They are sometimes called one way nuts, and for good reason as they only go on one way. Since these lock nuts do not have any nylon insert, and are entirely metal, they are especially useful in high temperatures.

15. Slotted Hex Nuts

Slotted hex nuts are a fastener that has slots or notches in the sides. The slots are made to prevent loosening when a cotter pin is installed to lock it in place.

Slotted hex nuts are lower profile than castle nuts. Their slimmer design might be beneficial, i.e. in getting around space restrictions or minimizing the visibility of the locking mechanism.

16. Square Nuts

A square nut is a four-sided fastener with a flat or beveled top. The square appears to create more surface contact, which helps resist loosening over time, especially with vibration or movement. Square nuts generally are used with square headed bolts to give reliable connections.

17. Structural Heavy Hex Nuts

Structural hex nuts have a design that is the same as finish nuts, but they are purposely manufactured thicker and stronger. In addition, structural hex nuts are much more durable, making them ideal for structural applications where steel is joined together.

18. T-Nuts

A T-nut -also referred to as a tee nut -is a fastener often used with wood, particle board, or composites where you want the surface to stay totally flush.

If you look at the shape of the T-nut, it has a long, slender body, with a flat flange at one end, when looking at it from the side, it actually resembles the letter “T.” The primary difference about T-nuts is that they have three or four sharp prongs on the flange.

As you install the T-nut, the prongs grip into the material, which helps keep the nut in place, while also preventing it from spinning or pulling out.

This is an effective design, which makes T-nuts a great option any time you want a solidly mounted, hidden threaded insert in your woodworking and furniture projects.

Types of Nuts

19. Break Away or Shear Nuts

Shear nuts are a type of fastening hardware that is easily identified by its unique cone shape and hex grip section. Shear nuts are also distinctive for their security feature, that when installed, the hex grip portion will break off, when torque has been reached.

This leaves only the original cone to tamper with, making the fastener very difficult to mess with, or to remove with the use of other tools. Shear nuts are especially useful when security is based off of limited removal ability as it helps with non-removable intent.

20. Tri-Groove Nuts

The forward conical shape of tri-groove security nuts make the nuts very difficult to grab using everyday tools like pliers or adjustable wrenches.

Tri-groove security nuts can only be installed or removed with a special, purpose-built tool. This advantage adds an additional layer of security compared to other nuts, because it makes unauthorized removal much more difficult.   

21. Wing Nuts

A wingnut is a style of fastener characterized by two “wings” protruding from the fastener which allows for easy gripping and turning by hand.

This design removes the need for tools for installation or removal and is especially useful when frequent adjustments and disassembly are required.

What Are Bolts?

Bolts are vital mechanical fastening devices that fasten two or more elements together. They are most often made of steel or other strong metals, but are instantly recognizable as a cylindrical shape with a head at one end and screw threads on the other end.

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The head is not just a decorative feature; it’s where you apply torque to tighten and loosen the bolt when you accept or disassemble materials. The threaded end pairs with a nut or a threaded hole to lock everything in place to prevent unwanted movement.

You will be astonished at the differences in bolts, each specifically designed to with a certain task. For example, hex bolts have a six-sided head that you can grip with a wrench.

Carriage bolts have a round head and a square neck to keep them from spinning while you tighten them. This feature is helpful when working with wood.

Lag bolts are intended for heavy-duty wood applications and have a square head or hex head. The end of a lag bolt looks like a spade, which means it can dig in for superior holding power.

Bolts are everywhere from the construction of buildings to automotive projects and manufacturing. Bolts have a reputation of strength and dependability, which is why they are the go-to fastener used to hold together machinery, buildings, or any other significant structure.

Because bolts are frequently exposed to the weather, they are made with some protective coating to prolong life and reduce rust.

As you search for fastener options, you will see that bolts are typically considered some of the most versatile types of fasteners available. Bolts come in different shapes and sizes for different materials and strength.

The differences usually come down to thread type, length, and head style. By altering the combination of thread type, length, and head style options, manufacturers have options for almost every conceivable purpose.

Generally when you use bolts to fasten objects, you will need a drilled hole and a like nut, or threaded component. Remember, unlike screws, bolts are not tapered which can make a difference when fastening two materials together.

Also, do not worry about the ever-changing terms used to describe fasteners; most people tend to use the terms “bolt” and “screw” interchangeably; However, the most important detail when fastening is which fastener you are using for the intended job, not which term was used in a website description.

Types of Bolts

Different kinds of bolts include Carriage Bolts, Hex Bolts, U-Bolts, Lag Bolts, T-Head Bolts, Socket Head Bolts, Shoulder Bolts, Penta-Head Bolts, Round Head Bolts, Flange Bolts, Double End Bolts, machine screws, Toggle Bolt, U-bolt, J-Bolt, Bolt etc.

Types of Bolts

1. Carriage Bolts

Carriage bolts are uniquely designed for security because of their self-locking characteristic. Look for the smooth domed heads that are flush against the surface.

The ingenious thing about carriage bolts is that you can only take it off the nut side; there is no way to grip the head from the outside.

The square portion of carriage bolts is just below the domed head. When you push the bolt through a material that has been prepped with a square hole, it slides into the square and holds it perfectly.

This holds the bolt and prevents it from spinning when you tighten the nut from the other side. Therefore, you do not need to hold the head with a wrench; this makes it easy and secure.

2. Hex Bolts

Hex bolts—sometimes called hexagon head bolts or simply hex head bolts are one of the most common types of fasteners available in both inch-based and metric sizing.

As the name indicates, hex bolts have a six-sided (hexagonal) head, which can be tightened or loosened with a common wrench or socket.

There are a couple styles of hex bolts: some are fully threaded to the head, some have smooth (unthreaded) shoulder just below the head.

They can be used for many applications (such as joining wood to wood, metal to wood, and metal to metal).

Hex bolts are often worked with hex nuts, and some may use washers. The washers can be helpful especially if fastening to softer materials, because the washer can help to protect it from being crushed while tightening the bolt.

A note about terminology: when a bolt has a washer face under the head and a chamfered (slightly round) end, it is usually identified as a hex cap screw. These two features are not found on standard hex bolts.

3. U-Bolts

U-bolts are a specific type of fastener with a U-shape over the majority of its length and a threaded end on both arms of the bolt. The threaded portion can be used for attaching mounting plates or nuts to secure the items in place.

While typically a smooth, semi-circular piece, U-bolts can be squared in appearance depending on the intended application.

Often, U-bolts offer only partial threading, as their intended purpose is to clamp and secure objects in place.

You can typically find U-bolts in all sorts of applications, some examples are as structural support mounts for pipe, in automotive applications such as securing drive shafts, exhaust, and more!

Some manufacturers add rubber coatings to U-bolts to reduce wear which occurs with metal on metal contact.

In addition, some U-bolts come with thick rubber gaskets to absorb any vibrations and to quiet any noise – this can be a practical feature in applications where silence is valued.

There are also non-metallic alternatives, which can prevent electrical hazards if there is a risk that a fastener could contact electrical conductors.

4. Lag Bolts

Lag screws are among the strongest fasteners available today. They are designed for demanding applications and are used to join large pieces of lumber or other materials that need to bear heavy loads.

Standard wood screws, for example, self-drilling screws or sheet metal screws are considerably smaller and will be more weakly formed than lag screws.

The lag screws may start at lengths of one inch or more, and would have thicknesses of a minimum of about a quarter inch. Obviously, lag screws have advantages whenever a project requires securing weighty materials under greater loads or stress.

5. T-Head Bolts

T-head bolts, which are also called T-slot bolts, are equipped with a head that permits slippage into a slot/recess. The way this head is shaped allows the bolt to be held in place, meaning it won’t rotate as you tighten the nut. This is a small detail, but it matters in some configurations.

In many cases, there are applications for the T-bolt where you simply can’t get to both sides of the fastener. For example, consider securing a fuel tank; in many cases, you don’t always have the luxury of being able to work both sides of the fastener, so you need a bolt that can be installed in one direction only.

The T-slot version takes this even further; it can be installed anywhere on the track of a machine T-slot and allows you to properly fit and fasten components where you want them.

This flexibility is particularly valuable if you’re dealing with equipment needing to be repositioned quickly and/or repositioned with precision.

6. Socket Head Bolts

Socket head bolts are often used for a variety of projects because of their versatility and ease of installation. A socket head bolt, just like a regular bolt, has a head and shank.

The head is recessed, which is a major difference in its design from a standard bolt, which has a conventional head. The recessed head means that the fastener can be tightened with an Allen wrench or male hex socket head tool.

If you’re like most people, you may be familiar with the cylindrical head shape of socket head bolts; however, there are actually a number of different head styles or shapes.

Sometimes you will see them in a flat bald, or countersunk head, or even a dome style or button style head. The shape you choose will really depend on your build.

As a side note, one of the main benefits of the deeper recessed Allen socket is that you can put more torque on a socket head bolt without the worried of stripping out the head. This is advantageous for any build where a tight, secure fit is needed.

You may hear socket head bolts referred to as socket head cap screws in specifications or if you’re purchasing them from suppliers. The terms socket head bolt and socket head cap screw are often used interchangeably, which can get confusing for some people, so it is helpful to have both terms in your vocabulary.

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7. Shoulder Bolts

Shoulder bolts, or stripper bolts, are unique because their threaded section is much smaller than the smooth Section, or shoulder, located between the head and the threads of the bolt.

Shoulder bolts are very important to applications where something must spin or move freely. Fairly commonly, shoulder bolts are used as shafts or axles to permit rotating parts, such as bushings or bearings, to work properly with the least resistance.

8. Penta-Head Bolts

The penta-headed bolts are a suitable example of tamper-resistant fasteners. They are commonly used for applications where there was a need to prevent unauthorized removal or loosening by individuals who have access to standard tools.

Due to the polygonal pentagonal shape of the bolt head, standard wrenches and socket sets in a standard toolbox won’t allow the head to turn. This reduces the ability of someone without a proper special tool to manipulate the tamper-resistant bolt.

9. Round Head Bolts

The visual resemblance of round-head bolts and carriage bolts similarity is misleading since the difference is that round-head bolts do not have the square section beneath the rounded head. Round-head bolts are usually only used on wooden structures.

Because wood is a relatively soft material, the round head can interface into the surface slightly. This creates friction between the bolt and the wood to hold the bolt so that when you are tightening the nut on the other side that the bolt will not spin.

Types of bolts

10. Flange Bolts

Characterized by the flange, or washer-like rim, below the head of the bolt, flange bolts are a type of fastener that helps to distribute clamping force over a greater area, reducing the risk of damaging mating surfaces.

Flange bolts are commonly found in plumbing and auto assembly applications, where reliability and durability play a critical role.

Generally, flange bolts are made from steel or stainless steel and are available with either fine or coarse threading, and also in a variety of material grades.

Depending on the application, the flange can either be smooth or serrated. The serrated flange provides additional grip to better hold the fastener against the mating surface.

11. Double-End Bolts

Double-end bolts, or stud bolts, are distinctive fasteners with threads on either end of the stud but no head. One end of each is meant to be screwed into a pre-tapped hole with the same threading, which locks the stud in place. The other end is exposed and has threads for a nut to be secured.

The design of a double-end bolt could cause it to be mistaken for a threaded rod; however, there are a couple of relevant distinctions.

Double-end bolts are not typically threaded along their full length; they are threaded on both ends, where each side has its own designated threading, which may or may not be the same.

In some particular instances, such as in the above example in the image, stud bolts may have a screw thread on one side, instead of a standard bolt thread on both, which alters the functionality slightly, depending on the application.

12. Machine Screws

A machine screw is considered a screw or bolt with a flat point at its end. There are many drive styles and head shapes to choose from, making them useful for many applications.

Machine screws are most commonly fastened into tapped holes, but can also fasten with nuts and washers. In some situations, they are referred to as “stove bolts” or simply “stovers.”

What Is Locking Nut?

A lock nut, or locking nut, is a nut that is designed to stay in place even when experiencing torque or vibration. Lock nuts are basically just a nut a circular piece of metal with internal threads; however, there is more development to make sure components do not loosen on their own or by being in an assembly.

With nuts (not lock nuts), the only thing to do with a nut is clamp the head of the screw or bolt, and hold the assembly rigid and not provide any unwanted axial slippage.

The problem comes to be where the assembly experiences continual, or constant vibration, and an external force – operational vibration – will loosen a normal nut, and damage has been done to the application.

That condition is where a lock nut fits into a solution; it has the design and development to allow it to live in such conditions, but also helps assist in keeping things fastened.

Lock nuts fall into two general groups: friction lock nuts and positive locking nuts. The friction type of lock nut provides a greater increase of resistance to turning, so you will find the friction lock nuts will require a bit more torque than other nuts to both tighten and loosen.

In fact, if you were to count the torque you apply before they will even begin to clamp down on a part, you would see you are applying more torque before they even start to “move” in assembly – that can be bad in assembly, if you use long threaded rods or something similar.

A few common types of friction lock nuts are the castellated nut, distorted thread lock nut, and the interference thread nut. The friction is a function of the relatively small change in shape of the nut, or arrangement of the threads to provide more “grip” in resisting loosening.

The positive locking nuts do not fully rely on friction. Therefore, the positive lock nuts can turn easily when tightening and loosing the nut, however, you will want the nut to stay put, and it is secured using a positive engagement, such as a small hole that allows a pin to, or similar, to ensure you locked the nut in place. Purely positive locking nuts provide a faster assembly and, when positively locked, are more secure.

A few common examples are slotted nuts and nylon locknut. Each will provide its own way to ensure things remained in the intended position – particularly when the condition becomes difficult.

FAQs.

What are Nuts and Bolts?

The bolt consists of a head and a cylindrical body with screw threads along a portion of its length. The nut is the female member of the pair, having internal threads to match those of the bolt. Washers are often used to prevent loosening and crushing. See also nut; washer.

What Are Nuts and Bolts Used For?

Both bolts and nuts are a type of fasteners used to join two objects or materials together to secure the object. These tools can prevent axial movement.

When Were Nuts and Bolts Invented?

The first nuts and bolts appeared in the middle 1400’s. The bolts were just screws with straight sides and a blunt end. The nuts were hand-made, and very crude. When a match was found between a nut and a bolt, they were kept together until they were finally assembled.

What is the difference between nuts and bolts?

A nut is a component that fits over the end of a bolt and helps it hold objects in place. A bolt is a non-tapered fastener that uses a washer and nut to hold objects together. A screw is a tapered fastener that mates with an existing thread or creates its own thread in a material as it turns.