Nuts and Bolts: Definition, Types, Sizing, Manufacturing, Applications

In this article, we will learn all about nuts and bolts along with the definition, meaning, types, applications, advantages, disadvantages, etc. Let’s explore!

What are Nuts and Bolts? Definition & Meaning

Nuts and bolts are the smallest tools with the most incredible benefits. There would be no mechanical construction if these two tools were not there. They are very small in size, but they are the ones holding the whole machinery together. Before starting any mechanical task, one must know what nuts and bolts are, how to use them, how they are made, which material is best for them, and how many different types of nuts and bolts are there.

nuts and bolts definition types sizing applications basics
Nuts and bolts definition types sizing applications basics

Talking about nuts and bolts. Let us discuss them separately and see how these tools work together.

What are Nuts? Meaning

Nut Definition

A nut is a small rounded metallic ring. Talking about the nut’s shape, the nut is not a mere round metal, but it is shaped very differently from other basic round metals.

  • It is fundamentally shaped as a ring with a hole inside. Its outer surface is not round all the time.
  • Instead, it may be hexagonal as well.
  • The inner side of the nut is round with a proper radius or diameter.
  • The inner circle is corrugated. It is shaped so that it has layers inside that play an essential role in making its grip even stronger.

Construction of Nuts

  • The hollow inner circle of the nut is always constructed to have grooves or threads inside it.
  • The nuts are strategically designed in this way. These groves or threads increase the locking ability of the nuts.
  • It remains fixed while holding the two parts.
  • These groves help in increasing the tightening ability of the nut as well.
  • The mechanic has to use the screwdriver opposite these groves to loosen up the nut.

Shapes & Sizes of Nuts

The nuts are available in different shapes and sizes. From shapes, it means that the outer surface of nuts may be circular, hexagonal, and in various shapes.

  • The inner circular portion of the nut is not always the same.
  • The main difference between different types of nuts is that their sizes vary from each other.
  • Their different sizes are estimated from the radius or diameter of their inner circle.
  • Every instrument, machinery, or bolt requires a nut according to its size.
  • If they are small, then the nuts with small size would work perfectly with them.
  • But, if their size is large, the nuts with a larger diameter or radius would make a perfect fit.

The outer surface of the nuts is made, keeping many points under consideration. The outer shape determines how fixed a nut would remain in its place. Moreover, it also determines the amount of wear and tears it wild case while one loosens up the nut. It is because of the vertices; more the area is in contact with the nuts. That’s why the hexagonal outer shape is considered the ideal shape of the nut.

The nuts are used and adjusted with the bolts with the help of different tools. Mainly wrenches are used to tighten and loosen the nuts. The opening size of the wench depends upon the size of the nuts. Wrenches are available in all sizes, from very small to very large extent.

What are Bolts? Meaning

Definition of Bolts

A bolt is a fastening tool used with the nut to hold the two things or parts of the machine.

  • A bolt is always used with a nut.
  • Without the nut, the bolt is useless, and the same is the case with the nut.
  • The structure of the bolt is quite different from the structure of the nut.
  • It is manufactured in such a way that its body shape gets fixed with the nut from each and every proportion.

Shapes of Bolts

Talking about the shape of the bolt, it has a cylindrical body ahead.

  • The cylindrical part of the body is called the shank of the bolt as well.
  • It may come in different dimensions depending upon its usage.
  • The shank may be longer or shorter in length.
  • It may be thick or thin in width.
  • It all depends upon the type of hole in which the shank of the bolt has to be inserted and the parts that it has to hold or fix together.

Shank of Bolts

  • The shank of the bolt is not smooth like the hammer nail.
  • Instead, it is very rough in its design. Here are grooves present on the shank of the bolt.
  • Those grooves are spiral and carved in a way that they automatically support the streamlined forward current.
  • The pattern of the tracks makes a bolt specific for a specific type of nut.
  • This is because the grooves are made; keeping the inner circular threads of the nut another same size under consideration.
  • The thickness of the cylindrical shank of the bolt is also set by observing the diameter of the inner circular hole of the corresponding nu of the similar size under consideration.

Head of Bolts

The head of the bolt also comes in different shapes. The shape of the head of the bolt depends upon the type of nut it is paired with. The head shape of the bolts is mainly similar to the outer form of the nut so that both the tools complement each other. Moreover, those similarities in their shapes guarantee more fixing power of nuts and bolts.

The streamlined forward grooves of the bolt help it to slide inward into the holes. The nuts are then fixed with the head of the bolt in a circular motion and are fixed to the extent that they become immovable. By this action, both the nut and bolt help to hold the two parts together.

Different tools are used to loosen up a bolt. Those tools include the wrenches and the hammers. The wrenches and hammers are available in different shapes and sizes according to the bolts’ shapes and sizes.

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Different Types of Nuts and Bolts

There is no standard type of nuts and bolts. Every machinery or tool has a different requirement. Sometimes the engineers need to join very small parts either with each other or with any stationary art or wall. At this point, the more preferable nuts and bolts would be those which are small in size and have the strength to carry the load as well.

In contrast to this situation, in heavy machinery or bigger projects, the mechanics need relatively larger nuts and bolts so that they can join the parts effectively and are not easily loosened.

The mechanical properties of nuts and bolts also play a very important role. As discussed earlier, the outer shape of the nut decides how much wear and tear there would be in the case of loosening that nut. So the mechanics and the engineers buy the nuts and bolts according to the requirements of their projects. Let us discuss the different types of nuts and bolts.

Types of Bolts

The types of bolts are hereunder:

Hexagonal Bolt

As the name illustrates, the hexagonal-headed bolt is the one in which the bolt’s head is shaped to form a hexagonal structure.

hexagonal bolt
Hexagonal bolt
  • The hexagonal shape of the bolt’s head ensures the good tightening ability of the bolt.
  • It is one of the most common types of bolt. It is designed so that when someone tries to loosen the nut, the bolt does not rotate.
  • Instead, it stays at its place.
  • The shank is designed to make the upper part of the shank a smooth cylinder, while the two-third portion of the shank is covered with spiral grooves.

Square Bolt

As the name suggests, the head of this bolt is given a square shape.

square bolt
Square bolt
  • This square-shaped head also ensures that the tightening ability of this bolt is excellent.
  • Moreover, less the vertices, less is the damage while loosening.
  • So this type of bolt is very safe to use in very sensitive areas of the machinery.
  • The head of the square-headed bolt is fixed in the square-shaped neck cross-section in case of any outward projection of the bolt. It prevents the bolt from rotating from its place.
  • The shank of this bolt is quite differently designed.
  • The upper half part of the shank is smooth, while the lower part has grooves.

Cheese Headed Bolt

This bolt is quite different in shape than the bolts mentioned above. This type of bolt is used where the hole or the space for the projection or insertion is very limited.

cheese headed bolt
Cheese headed bolt
  • The mechanic has to put in some extra effort in order to fix this bolt into place.
  • There is a groove in the head of the bolt.
  • A screwdriver is mainly used to operate such bolts.
  • The pointed part of the screwdriver is locked in the groove of the bolt to rotate and insert it in the required places. There is a pin inserted just below the head.
  • That pin prevents it from rotating. These bolts are used in connectors and eccentrics etc.

Round Headed Bolts

These bolts have plain round heads without any extra groove or shaping. They are used to give a better and tidy look to the objects or machines.

round headed bolts
Round headed bolts

There is a very solid round nut-like piece fixed just below its head on the shank. This piece stops it from rotating or moving from its place.

Bolts with T-heads

They are commonly known as T-headed bolts. They are used in the machine tables mainly. The T-shape of the head helps in securing the things in their place.

bolts with T heads
Bolts with T heads

The machine tables already have space for the T-shaped head. The neck of this bolt is in a square shape that prevents it from rotating.

Bolt with Countersunk Head

This bolt is unique in its shape. Its head is not bulged out in a specific shape; instead, the head of this bolt is designed to lie on the same level of the surface of the object or machine.

bolt with countersunk head
Bolt with countersunk head

In this way, they become less prominent, which adds to the factor of appearance of the machinery. It has a hole or groove sunken in its head.

Stove Bolt

This bolt is used for particular purposes. It has a groove or slit in its rounded head/ this bolt is fixed and loosened with the help of screwdrivers.

stove bolt
Stove bolt

Hook Bolt

It is a very different and special type of bolt. It is not used for permanent fastening. Instead, it is used for temporary fastening. It is mostly used in concrete.

hook bolt
Hook bolt

Some parts or areas are so weak that drilling a single hole can cause a significant threat to their structure. The main benefit of this bolt is that it is easily fixed in a place without digging a hole.

Types of Nuts

Different types of nuts are mentioned as follows;

Hexagonal Nut

As the name illustrates, the outer shape of this nut is a hexagon. At the same time, the inner shape of this nut is a circle with threading or grooves.

hexagonal nut
Hexagonal nut
  • This nut is always paired with a bolt that has a hexagonal-shaped head.
  • In this way, the nut and bolt can be fixed with each other providing a more remarkable locking ability.
  • This is the most common type of nut used in kinds of machinery or other projects.
  • It is easily loosened with the help of a wrench.

Square Nut

As the name illustrates, this nut has the outer surface shaped as he squares with an inner circular surface. The inner circle also has grooves that help me slide on the threads or grooves of the bolt’s shank.

square nut
Square nut

This square nut is used with the square-headed bolt.

Ring Nut

This nut looks like a ring in the first look. Its outer and inner surfaces are both shaped in a circle. The outer circular shape has three slits at an equal distance.

ring nut
Ring nut

The c spanner rotates these nuts by fixing its tips into the slits of the nuts.

Cap Nuts

They are very different from the commonly used nuts. They have an inner threaded circle while the outer surface is shaped like a hexagon.

ring nut
Ring nut

There is a cap fixed on the top of the hexagon. These nuts are used in smoked box locomotives.

Standard Nut and Bolt Sizing

The standard nut range in size from #0 to #14, and 1/4″, 5/16″, and 3/8. The most common style is Hex, and it is available almost everywhere. Similarly, there are standard sizes for the bolts as well. These are the bolt sizes that are most commonly used all over the world. Manufacturers use 12mm, 14mm, 17mm, and 19mm bolts most of the time.

The manufacturing process of bolts and nuts is as enjoyable as these tools themselves are. Let’s discuss their manufacturing process in detail.

Manufacturing of Nuts and Bolts

Manufacturing of Bolts

The bolts are made up of steel metal. Steel itself has many benefits. It is intense as well as affordable. It is readily available as well. The manufacturing process of the bolts involves the following steps

  • The steel wires are uncoiled and are straightened
  • Then they are cut into the desired length
  • At room temperature, the steel is molded into the desired shape
  • The bolt head is formed by exposing the steel to high pressure
  • The cutting of the steel forms the threads
  • Afterward, the steel is exposed to high heat so that it can harden itself up
  • To prevent the corrosion of steel, it is then plated with zinc

Manufacturing of Nuts

Nuts are also manufactured through some similar processes. The steps involved in the mechanical manufacturing of nuts are given as follows

  • The steel wires are straightened
  • They are made soft so that they can be molded into the desired shapes
  • The steel wires are treated with sulphuric acid
  • They are given the shapes of nuts
  • The threading is dined by rolling and cutting
  • The nuts are then exposed to extreme heat to harden the steel
  • They are zinc plated to prevent their surfaces from corrosion

Applications of Nuts and Bolts

Nowadays, there is no such thing or place or field where these nuts and bolts are not used. They are the essential elements of construction. They are required and used everywhere. We use so many machines in our daily lives, and these nuts and bolts are used in almost every one of them. Some of the significant applications of nuts and bolts are in different places and fields, mostly related to construction, mechanics, and engineering.

  • Nuts and bolts are used in wind farms to install hefty machinery and fix their inner parts.
  • They are used in the machinery of solar thermal plants.
  • The big boilers and other machinery in nuclear power plants are installed with the help of nuts and bolts.
  • The nuts and bolts have a significant application in the construction and application of railway tracks.
  • One track is fixed to the other tracks with the help of huge nuts and bolts.
  • The tracks are fixed to the ground with the use of nuts and bolts.
  • They are used in the construction process of ship buildings.
  • The machinery is installed in them and fixed with the help of nuts and bolts.
  • They are used in photovoltaic plants to adjust and set the solar panels.
  • They are used in the water pipelines to join the pipes and hold the different connections together.
  • Huge nuts and bolts are used in the pumps and valves.
  • The water pumps and the gas valves are also fixed with the help of nuts and bolts.

Advantages of Nuts and Bolts

These nuts and bolts are a part of our lives. All the newly invented machines have the usage of nuts and bolts in them.

  • The main advantage of nuts and bolts is that they are very common in use and are readily available everywhere. These are included in those essential tools with which everyone is familiar.
  • The second advantage of using nuts and bolts is that they are very simple to install. One does not need to go for special guides in order to understand the method to install them.
  • They are very easy to handle and install. One can do it by himself or with the help of some other fellow easily in case of huge nuts and bolts. And same is the case with the loosening of nuts and bolts. The small nuts and bolts are easily loosened with the help of hammers only. The wrenches are also used to loosen the nuts and bolts and are very easy to handle.
  • The third important factor that adds to the advantages of using nuts and bolts is their resistance to corrosion. When these nuts and bolts are manufactured, they are plated with a coating of zinc solution that prevents the steel from corrosion. This leads to its longevity and ensures maximum strength for a long period of time.
  • The fourth advantage is that they do not require heat treatment during the process of fastening. Most of the time, the fastening tools are provided with heat treatment to ensure that they are correctly fixed, but such is not the case in the usage and installation of nuts and bolts.

Disadvantages of Nuts and Bolts

Every picture has two sides. The same is the case with the sage of nuts and bolts. They have a few disadvantages as well.

  • Firstly, they require the drilling of holes wherever they are used. The machines’ spare parts come with holes and spaces in them for the nuts and bolts. But if something is to be fixed with the wall or in wood, it requires drilling a hole, which can weaken the wall.
  • Secondly, the nuts and bolts are not installed by working on one side. The mechanic has to work from both sides in order to install them. Sometimes in the case of larger nuts and bolts, it may require the presence of a helper to help the mechanic use the nuts and bolts.
  • Thirdly, they are exposed to continuous vibration, which causes them to weaken very quickly. Moreover, if they are not appropriately coated, they catch rust very quickly. This rust can lead to the rusting of the other parts of the machinery as well.


The nuts and bolts are no doubt very essential and basic parts of everyone’s tool kits. They come in various sizes and shapes to match the requirement of the machinery. They are very strong and are of great quality. One just needs to put some effort while installing them in the machinery. Refer our YouTube VideosOpens in a new tab.

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Hello Everyone! We, Rituparna Guha & Firan Mondal, are delighted to present our Mechanical Engineering articles. We will capture all types of articles and try to explain in the simplest way with a lot of diagrams! Happy Reading....

One thought on “Nuts and Bolts: Definition, Types, Sizing, Manufacturing, Applications

  1. I like that you talked about how the hexagonal shape of the bolt’s head would ensure the good tightening ability of the bolt. I am planning to repair some things in my garage and I definitely need some bolts for it. So, I’ll shop for some hex head bolts later.

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