Different Types of nuts and bolts With Pictures & pdf Applications

A bolt is composed of two parts: 1. a shank and 2.a head. The shank is the cylindrical portion of the bolt. The shank is threaded for a sufficient length at the tail end to effectively engage with a nut. The shape of the head is determined by the purpose of the bolt.

A nut is a type of fastener with a threaded hole in it. To fasten various parts together, the nut is always used in conjunction with a mating bolt.

Eye bolts, wheel bolts, and machine bolts are examples of bolt types, while cap nuts, expansion nuts, and u-nuts are examples of nuts. This guide will explain the various types of nuts and bolts, as well as the various types of bolt heads.

Forms of the bolts

The following are some of the most commonly used bolts:

Hexagonal headed bolt

Hex bolts, also known as hexagon head bolts or hexagonal head bolts, are a popular type of bolt that come in standard dimensional inch and metric sizes. These bolts, as the name implies, have a hexagonal or hex head that can be tightened with a wrench or socket.

This is the most common type of bolt and is used for general fastening. The upper end of the hexagonal head is chamfered.

Another spanner is used to hold the bolt-head in place while screwing the nut on or off. The figure is showing a hexagonal-headed bolt.

A hex bolt can be threaded all the way through or have an unthreaded shoulder. Hex bolts are frequently used to connect wood to wood, metal to metal, or metal to metal. Hex nuts and washers are commonly used with hex bolts, with washers being especially useful when the material being joined is softer and may deform under the tightening force applied to the hex bolt.

When hex bolts have a washer face beneath the head and a chamfered end, they are sometimes referred to as hex cap screws. Hex bolts do not have these characteristics.

Square headed bolt

When the head is to be accommodated in a recess, this bolt is commonly used. This recess is square in shape to prevent the bolt from turning when the nut is screwed on or off.

When a square-headed bolt is to be used with its head protruding outside, it has a square-section neck. This prevents the bolt from rotating. This bolt is commonly used in shaft bearings. The figure depicts a square-headed bolt.

Square head bolts, like hex head bolts, are distinguished by their head shape, i.e., square. This head design facilitates tooling gripping, making installation easier.

Cylindrical or Cheese-Headed Bolt

This type of bolt is used when protruding corners are unacceptable and there is limited space for arranging the bolt-head. The rotation of the bolt is prevented by a pin inserted into the shank just below the head.

Cup headed or round headed bolt

The protruding portion of this pin fits into a corresponding groove in the adjacent piece. This bolt is commonly used in the big ends of connectors, eccentrics, and other similar devices.

This bolt is used when projecting is undesirable and a better appearance is required.

It is usually equipped with a sung forged on the shank just below the head, as shown in the figure. To prevent the bolt from rotating. This bolt is used in the construction of tanks and certain locomotive components.

This type of bolt is oval in shape and is commonly used in the Carpenter Shop.

It is also referred to as a Rail track bolt.

T-headed bolt

T-head bolts, also known as T-slot bolts, have a head design that allows them to be inserted into a slot or recess, securing the bolt in place and preventing it from turning when the securing nut is tightened.

T-bolts are used in applications such as securing fuel tanks where access to both sides of the fastener is not always possible. T-slot T-head bolts can be fed into a channel in a machine called a T-slot track and used to secure an object at any point along the channel’s length.

This type of bolt is used to secure clamps, vices, and other machine tool accessories to machine tool tables.

T-slots are provided on the tables to accommodate the T-heads. The neck of this bolt is usually square in section to prevent the bolt from rotating. The figure depicts a T-bolt.

Countersunk-Headed bolt

Countersunk Bolts are flat headed bolt fasteners with hex sockert drive into the head. Countersunk bolts have a cone type neck with flat head. Flat Head Hex Socket Bolts, Flat Head Socket Cap Bolts are other alias of hex head bolts.

This type of bolt is used when the bolt’s head must not project above the surface of the connection piece.

It may be provided with a snack or a neck to prevent the bolt from rotating.

Countersunk bolts are used when a smooth surface is required. Common applications include bridge decking, walkways, and railing.

Special purpose bolts

The following are some examples of special-purpose bolts.

Stove bolt

Stove bolt heads are typically flat and slightly tapered on the bottom, allowing them to be countersunk, or rounded on the top and flat on the bottom. The bolt head is usually slotted for use with a standard screwdriver, though some bolts have Phillips heads.

A screwdriver is used to screw the bolt into a nut. This is used for assemblies where precision is not critical and it is preferable to have the bolt head flush with the surface of the work.

Stove bolts are made of sheet metal and have a slotted head. They are commonly used in the assembly of wood-burning stoves. Stove bolts are also known as machine screws because they have a machine thread and a round, flat, or truss head.

Carriage bolt

This is used to fasten wooden parts together or metal parts to wood. It has a squared portion directly under the head to prevent the nut from rotating when tightened or loosened. The figure depicts a carriage bolt.

Carriage bolts have a domed head, which prevents loosening from one side. An enlarged head shape also prevents the bolt from being pulled through a wooden structure.

Eye bolt

It is a bolt hooked at one end and threaded at the other to receive the nut.

The hook bolt, shown in Fig., is used in concrete for semi-permanent fastening.

This is also used when there is no room for a bolt hole through one of the connecting pieces, or when a bolt hole would seriously weaken a piece. As a result, hook bolts are used to secure shaft hangers to the flanges of joists and girders.

Expansion bolt

This bolt is used to secure parts to brick, stone, or concrete walls and floors. The bolt has an internally threaded split sleeve that is inserted into a hole in the wall and then expanded by screwing it in. This is depicted in Fig.

Expansion bolts can be used to secure heavy objects to walls or floors.
Can handle both vertical and horizontal loads.
Tightening the bolt causes the nut on the opposite end to pull into the shell, expanding it outward and wedged it inside the hole in the wall or floor.

Foundation or rag bolts

This distinctive foundation bolt has a tapered body with grooves on all sides and a square or rectangular cross-section. Similarly to the bent foundation bolt, it is necessary to allow the rag bolts to set in lead before allowing the entire assembly to set in concrete.

The rag bolt, shown in Fig., is used to secure the stone concrete foundation; the head is wider at the bottom than at the top, and it is led into a tapered hole.

The tapered head is cut unevenly (jaggedly), and moulted lead or sulfur is poured into the taper hole to fill the space between the lead and the stone or concrete, depending on the case. Four parallel bars or keys are used in addition when great strength is required.

Eye bolt

The eye-bolt depicted in Fig. is commonly used for lifting. It is screwed or turned into a threaded hole on the machine’s top.

Electric motors and medium and lightweight machinery are outfitted with one or more eyebolts to allow for easy lifting and movement by an overhead crane.

Eye bolts can be used to connect rigging, anchoring, pulling, pushing, or hoisting applications. Although eye bolts are widely used in industrial applications, they are frequently misunderstood or misused.

Stud

A threaded rod, also known as a stud, is a long rod that is threaded on both ends; the thread may extend the entire length of the rod. They are intended to be used under tension. Threaded rod in bar stock is frequently referred to as all-thread.

A stud is depicted in Fig. as a plain piece of cylindrical steel that is screwed at both ends. It does not have a head like a bolt. The nut-end is threaded slightly longer than the thickness of the nut or nuts to be used.

The other end is known as the metal end. It is threaded for a length at least equal to the stud’s diameter. When a bolt is not available, a stud is used in its place. Studs are commonly used to cover engine cylinders.

U bolt

U-bolts are fasteners shaped like the letter U that have two male threads, one on each end of the bolt, on which a mounting plate bracket and attachment nuts are attached. While the majority of U-bolts have a semi-circular profile, some are squared off.

Because they function to clamp an object in place, these fasteners are typically not fully threaded. They are used in a variety of applications, from supporting pipe to drive shafts and exhaust systems in automobiles. Some designs include a rubber coating to prevent wear from metal on metal movement.

Other U-bolt designs include thick rubber gaskets to reduce vibration and control noise. Non-metallic designs are also available for use in situations where the U-bolt may come into contact with an electrically powered conductor.

Other U-bolt designs include thick rubber gaskets to reduce vibration and control noise. Non-metallic designs are also available for use in situations where the U-bolt may come into contact with an electrically powered conductor.

Lag bolt

Lag screws, also known as lag bolts, are among the most durable fasteners. These incredibly strong fasteners are typically used to connect heavy lumber or other heavy materials that are bearing a heavy load. These screws are distinct from standard wood, self-drilling, and sheet metal screws.

Lag screws are among the most durable fasteners. These incredibly strong fasteners are typically used to connect heavy lumber or other heavy materials that are bearing a heavy load.

These screws are distinct from standard wood, self-drilling, and sheet metal screws. Lag screws are enormous in size when compared to most ordinary screws. The majority of lag screws are at least one inch long and 14 inch thick.

Socket head bolt

Socket head bolts have a recessed head and are tightened with an Allen wrench or hex socket tool. Depending on the application, the head style of these bolts can range from a cylindrical profile to a flat-head countersunk style to a domed button head design.

The deeper recessed Allen socket head allows you to apply more torque to these fasteners while reducing the risk of stripping or damaging the head. Depending on the supplier, socket head bolts are also known as socket head cap screws.

Types of nuts

Nuts come in a wide range of shapes, sizes, materials, and thread patterns. While your choice of nut is somewhat constrained by the bolt, particularly in terms of size and threading, you should still choose the nut head shape and material that is best suited to your application.

Hexagonal nut

A hexagonal nut is a metal fastener with six sides. Most nuts are cut in a hexagonal shape because it appears to be the easiest to grasp. Nuts, in any shape or form, are almost always used to secure a bolt to another object. The collar insert of the nyloc nut is made of nylon.

“This is the most common type of nut used for general fastening when combined with a hexagonal-headed bolt. Figure shows a hexagonal nut.”

Square nut

A square nut is a nut with four sides. Square nuts, as opposed to standard hex nuts, have a larger surface area in contact with the part being fastened and thus provide greater resistance to loosening. They are also less likely to become rounded-off as a result of repeated loosening/tightening cycles.

A square nut, as shown in fig., is used with a square-headed bolt. The nut spanner may have a better grip on a square nut than on a hexagonal nut.

Ring nut

It has the shape of a ring with slots in the curved surface for a special c-spanner. The illustration depicts a ring nut. These nuts are typically used in pairs, with one acting as a lock nut and the other as a wing nut.

Cap nut or done nut

It is a hexagonal nut with a cylindrical cap on top to protect the end from corrosion. It also keeps leakage through the threads to a minimum. Cap nuts are commonly found in smoke-boxes and locomotives.

An acorn nut is a nut with a domed end on one side. It is also known as a crown hex nut, blind nut, cap nut, domed cap nut, or dome nut (UK).

A cap nut protects the threads beneath it while also providing a cleaner, more aesthetically pleasing appearance and improving safety in some applications.

Cylindrical or capstan nut

a nut resembling the head of a capstan and operated by a bar inserted into one of several holes around its periphery

This nut is cylindrical in shape and has tommy bar turning holes drilled into the curved surface.

Wing nut

A wingnut, also known as a butterfly nut, is a type of nut with two large metal “wings,” one on each side, that allow it to be tightened and loosened by hand without the use of tools.

The illustration depicts a wing nut. This nut is used where it must be adjusted frequently and can be easily operated with the thumb and a finger.

Locking of Nuts

Even in the best of fits, a small working clearance exists between the threads of a nut and a bolt when a nut is tightened over the bolt.

The nuts and bolts used in the moving parts of machinery will be subjected to continuous vibration and, in some cases, required to carry varying axial load, such as the crossheads and connecting rods of an engine.

Because of the working clearance between the mating threads, the nut tends to work loose or unscrew on its own under these conditions.

As a result, a serious breakdown is possible. To prevent this, some method of preventing the nut from unscrewing is required. Positive and friction locking devices are the two types of nut locking devices. However, if the threads of the nut and bolt are a good fit, the tendency of unscrewing is reduced.

Positive locking methods use a split pin, a screw, a lock plate, or a tab washer to secure the nut. To lock the nut in the friction method, either an additional nut called a lock nut or a spring washer is used.

Split pin locking

The figure depicts the simplest method of locking a nut with a split pin. After the nut has been properly tightened, a small hole is drilled through the blot near the nut’s top face. The split pin is then inserted into the hole, and the split ends are opened to prevent it from coming out while in use.

The main disadvantage of using this type of locking is that the hole drilled in the blot significantly reduces its strength. The other, equally important, objection is that after continuous use, the split pin may not rest on the top face of the nut, reducing the locking effect.

A split pin, also known as a cotter pin or cotter key in the United States, is a metal fastener with two tines that bend during installation, similar to a staple or rivet. Another application of the term “cotter pin” is the “crank cotter pin,” which is used to secure bicycle pedal cranks to the bottom bracket axle.

How to install split pin

Insert the cotter pin into the bolt’s hole until the pin’s head rests against the bolt. Spread the prongs in opposite directions to secure the cotter pin, if desired with pliers. Cut excess length from either prong with diagonal cutters according to your application standards.

Set screw locking using groove nut

Penn to ring or grooved nut refers to a hexagonal nut with a cylindrical grooved collar at its lower end. As shown in the figure, the end of the bolt hole is counterbored to receive the cylindrical lower grooved portion of the nut. A set screw screwed through the nearest face of the workpiece secures the nut.

The set-projecting screw’s dog-end enters the groove in the cylindrical portion of the nut and prevents the nut from slackening. If the bolt hole is close to the nearest vertical edge, as in the case of marine engine connecting rods, this method of locking is possible.

This nut is used in conjunction with a separate collar when the bolt hole is not close to the vertical edge of the workpiece, as shown in the figure. The dowel pin screwed into the bearing surface prevents the collar from rotating.

Locking by a lock plate

This type of locking is used in heavy engineering work, such as connecting rods, wheel shafts, and so on. The figure depicts the empirical proportions of the lock plate. The nut is tightened first, and then the lock plate is inserted through the nut.

The plate is grooved in such a way that the hexagonal corners of the nut are received by the grooves in the plate at every 30° rotation. A tap bolt screwed into the plate secures it to the bearing surface. The assembly of the locking of a nut by the lock plate was depicted in the figure. The nut is prevented from slackening because it is held tight within the grooves of the lock plate.

Locking by a tab washer

The tab washer is a washer that has a rectangular projection. This method of nut or bolt head locking is appropriate when the nut or bolt head is close to the vertical edge of the workpiece.

After tightening the nut, the tab and the projecting portion of the washer are bent to bear against the vertical surface of the workpiece and one of the nut’s lateral faces or the bolt head.

Locking by a lock nut

The friction between the mating threads of the bolt and nut locks the nut in this type of locking. When a nut is tightened over a bolt, the lower flanks of the bolt’s threads come into contact with the upper flanks of the nut’s threads.


When another nut is tightened tightly over the lower nut, it tends to pull the bolt through. Because there will be no contact between the threads of the bolt and the lower nut, the upper nut will virtually take up all of the load, while the lower nut will simply function as a washer.

The upper nut is now held in place by a spanner. While pulling in the opposite direction with the lower nut. This causes the lower flanks of the lower nut’s threads to come into contact with the upper flanks of the bolt’s threads, resulting in a wedging action between them.

As a result, the lower nut acts as a lock nut. In theory, the lower nut, which is a lock nut, could be the thin nut shown in fig. However, because it required a special thin spanner to turn it, it is more common in practice to place the taking nut below the lock nut, as shown in Fig. In such cases, two nuts of equal thickness are sometimes used, as shown in Fig.

Locking by a spring washer

The washer is placed beneath the nut in this method of locking a coiled spring, as shown in Fig. When the nut is tightened, the spring force exerts an axial force on the underside of the nut, which is held in place by the friction grip. This prevents the nut from slackening.

For light classes of work, a single coiled spring washer will suffice. When the vibrations are high, a double or triple coiled spring washer is used.

Screw pin locking

A screw pin screwed in the bearing surface adjoining the nut and touching one of the lateral faces of the nuts, as shown in Fig. This type of locking is used when the nut is expected to remain unaltered for an extended period of time.