Home » Mechanical Engineering » List of 20 Different Types of Nuts and Bolts [with PDF]

List of 20 Different Types of Nuts and Bolts [with PDF]

Hey, today we’re going to discuss the various types of nuts and bolts and also go over how they work.

However, the primary use of bolts and nuts is to hold the components or objects in place. So without any more delay, let’s learn the different types of nuts and bolts with pictures.

Nuts and Bolts Types

A bolt contains two parts a shank and a head. The cylindrical portion of the bolt is known as the shank. The shank is threaded at the tail end for a sufficient length to engage with a nut effectively.

The shape of the head is depended upon the purpose for which the bolt is required. The nut is a type of fastener that has a threaded hole in it. The nut is always used in joining with a mating bolt to fasten various parts together.

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Types of Nuts and Bolts

Different forms and types of nuts and bolts are as follows:

Types of Bolts:

  1. Hexagonal-headed bolt
  2. Square-headed bolt
  3. Cylindrical or cheese-headed bolt
  4. Cup-headed or round-headed bolt
  5. T-headed bolt
  6. Countersunk-headed bolt
  7. Stove bolt
  8. Carriage bolt
  9. Hook Bolt
  10. Expansion bolt
  11. Foundation or rag bolt
  12. Eye-bolt
  13. Stud

#1 Hexagonal-headed Bolt

hexagonal headed bolt -Types of Nuts and Bolts

This is the most common bolt form and is used for general fasting purposes. The hexagonal head is chamfered at its upper end.

To prevent the rotation of the bolt while screwing the nut on or off, another spanner holds the bolt head—a hexagonal-headed bolt illustrated in the figure.

#2 Square-Headed Bolt

square headed bolt -Types of Nuts and Bolts

This bolt is commonly used when the head is to be accommodated in a recess. This recess is made of a square shape so that the bolt is prevented from turning when the nut is screwed on or off.

When a square-headed bolt is to be used with its head projection outside, it is provided with a neck of square cross-section. This prevents the rotation of the bolt. This bolt is commonly used in bearings for the shaft. A square-headed bolt is shown in the figure.

#3 Cylindrical or Cheese-Headed Bolt

cheese headed bolt -Types of Nuts and Bolts

This type of bolt is used where projecting corners are unacceptable, and the space for arranging the bolt head is relatively limited. The bolt rotation is prevented using a pin inserted into the shank just below the head.

The projecting part of this pin fits into a corresponding groove in the adjacent piece. This bolt is commonly used in big ends of connectors, eccentrics, etc.

#4 Cup-Headed or Round-Headed Bolt

round headed bolt -Types of Nuts and Bolts

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

It is usually provided with a sung forged on the shank just below the head, as shown in the figure. To prevent rotation of the bolt. This bolt is used to construct tanks and certain parts of locomotives.

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#5 T-Headed Bolt

T-headed bolt -Types of Nuts and Bolts

This type of bolt is used for securing clamps, vices, and other accessories to the tables of machine tools. The tables are provided with T-slots to accommodate the T-heads. The neck of this bolt is usually square in section to prevent rotation of the bolt A T-bolt is shown in fig.

#6 Countersunk-Headed Bolt

counter sunk headed bolt -Types of Nuts and Bolts

This form of a bolt is used where the head of the bolt must not project above the surface of the connection piece. It may be provided with a snack or a neck to prevent the rotation of the bolt.

#7 Stove Bolt

stove bolt -Types of Nuts and Bolts

A stove bolt has a round flat head which is beveled on the underside to fit a countersunk hole. It is provided with a slot on the head, as shown in the figure.

For screwing the bolt into a nut, use a screwdriver. This is used for assemblies where precision is of no great importance, and it is desirable to have the head of the bolt flush with the surface of the work.

#8 Carriage Bolt

carriage bolt

This is used for fastening wooden parts together or for fastening metal parts to wood it has a squared portion directly under the head to prevent rotating when the nut is tightened or slackened. A carriage bolt is shown in the figure.

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#9 Hook Bolt

hook bolt

The hook bolt, shown in Fig., is used in semi-permanent fastening in concrete. This is also used in cases where there is no room for a bolt hole through one of the pieces to be connected or in cases where a bolt hole would seriously weaken a piece. So the hook bolt is used for attaching shaft hangers to the flanges of joists and girders.

#10 Expansion Bolt

expansion bolt

This type of bolt attaches parts to brick, stone, or concrete walls and floors. Hee bolt has an internally threaded split sleeve which is slipped into a hole made in the wall and then expanded by running in the screw. This is shown in Fig.

#11 Foundation or Rag Bolt

foundation or rag bolt

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

The tapered head is cut unevenly (jagged), and molted lead or sulfur is poured into the taper hole to fill the space between the lead and the stone or the concrete, as the case may be. Where great strength is required, four parallel bars or keys are also used.

#12 Eye-Bolt

eye bolt

The eye bolt, shown in Fig., is commonly used for lifting purposes. It is screwed or turned inside a threaded hole on the top of the machine.

Electric motors and medium and lightweight machinery are equipped with one or more eye-bolt so that they may be readily lifted and moved by an overhead crane.

#13 Stud


A stud shown in Fig. consists of a plain piece of cylindrical steel screwed at both ends. It has no head like a bolt. The nut-end is threaded for a length slightly more than the thickness of a nut or nuts to be used.

The other end is called the metal end. It is threaded for a length at least equal to the diameter of the stud. The stud is used in place of a bolt when a bolt. Stud is commonly used to cylinder covers engine cylinders.

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Types of Nuts

In order to mack bolt and studs into effective fastenings, the nut is required. Nuts are usually in the form of hexagonal or square prisms. Besides these, the cylindrical and other form is used in a particular requirement.

  1. Hexagonal nut
  2. Square nut
  3. Ring nut
  4. Cap nut
  5. Cylindrical or capstan nut
  6. Dome nut
  7. Wingnut or thumb nut

#1 Hexagonal Nut

hexagonal nut -Types of Nuts and Bolts

This is the most common form of nut used for the general fastening purpose in conjunction with a hexagonal-headed bolt. A hexagonal nut is shown in Fig.

#2 Square Nut

square nut -Types of Nuts and Bolts

A square nut, shown in fig., is used in conjunction with a square-headed bolt. The spanner used for the nut can have a better hold on a square nut than on a hexagonal nut.

#3 Ring Nut

ring nut -Types of Nuts and Bolts

It is the form of a ring provided with slots in the curved surface for a special c-spanner. A ring nut is shown in the figure. These nuts are generally used in parts, one nut acting as a lock nut and the other.

#4 Cap Nut

cap nut

It is a hexagonal nut provided with a cylindrical cap at the top to protect the end from corrosion. It also prevents leakage through the threads. Cap nuts are commonly used in smoke-boxes locomotives.

#5 Cylindrical or Capstan Nut

cylindrical or capstan nut

This nut is cylindrical and has holes drilled in the curved surface for turning it with a tommy bar.

#6 Dome Nut

dome nut

It forms the cap nut having a special dome at the top as shown in the figure.

#7 Wingnut or Thumb Nut

wing nut or thunb nut

A wingnut is shown in the figure. This nut can be easily operated by the thumb and a finger and is used where it must be adjusted frequently.

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Methods of Nut Locking

#1 Locking of Nuts

When a nut is tightened over the bolt, a small working clearance exists between the threads of a nut and bolt, even in the highest class of fits.

The types of nuts and bolts used in the moving parts of machinery will be subjected to continuous vibration. In addition, sometimes, they are required to carry varying axial loads also, for example, as the crossheads and connecting rods of an engine.

Under such conditions, because of the working clearance existing between the mating threads, the nut develops a tendency to work loose or unscrew by itself.

This consequently may result in a serious breakdown. To prevent this, some means of locking the nut from unscrewing is necessary. The various locking devices for nuts are classified into positive and friction types. However, the tendency of unscrewing is reduced if the threads of the nut and bolt are of a good fit.

The positive locking methods use a split pin, a screw, a lock plate, or a tab washer to lock the nut. In the friction method, an additional nut called a lock nut or a spring washer is used to lock the nut.

#2 Split Pin Locking

The simplest method of locking a nut using a split pin is shown in the figure. After the nut has been finally tightened, a small hole is drilled through the blot close to the top face of the nut. The split pin is then inserted in the hole, and the split ends of the pin are opened to prevent it from coming out while in use.

split pin locking

The main objection to using this type of locking is that the hole drilled in the blot reduces its strength considerably. The other equally important objection is that after continuous use, swing to the stretch of the bolt, the split pin may not rest on the top face of the nut, which may reduce the locking effect.

#3 Set Screw Locking Using Grooved Nut

A hexagonal nut with a cylindrical grooved collar at the lower end is called Penn to ring or grooved nut. The end of the bolt hole is counterbored to receive the cylindrical lower grooved portion of the nut, as shown in the figure. Locking of the nut is done by a set screw screwed through the nearest face of the workpiece.

set screw locking

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

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

#4 Locking By a Lock Plate

This type of locking is employed in heavy engineering work, as in the case of connecting rods, wheel shafts, etc. The empirical proportions of the lock plate are shown in the figure. Initially, the nut is tightened, and then the lock plate is inserted through the nut.

The plate is grooved so that the grooves in the plate receive the hexagonal corners of the nut at every 30° rotation. The plate is fixed to the bearing surface by a tap bolt screwed into it. The figure shows the assembly of the locking of a nut by the lock plate. Since the nut is held tight within the grooves of the lock plate, the nut is prevented from slackening.

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#5 Locking By a Tab Washer

A washer provided with a rectangular projection is called a tab washer. This method of locking of nut or bolt head is suitable when the nut or bolt head is placed near the vertical edge of the workpiece.

tab washer

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

#6 Locking By a Lock Nut

In this type of locking, the friction between the mating threads of the bolt and nut locks the nut. When the nut is tightened over a bolt, the lower flanks of the bolt threads will be in contact with the upper flanks of the nut threads.

lock nut

When another nut is screwed down hard over the lower nut, it tends to pull the bolt through the lower nut. This virtually makes the upper nut take up all to load, While the lower nut to function simply as a washer since there will not be any contact between the threads of the bolt and the lower nut.

Now the upper nut is held by a spanner While the lower nut is pulled in the opposite direction. This cause the lower flanks of threads of the lower nut to come in contact with the upper flanks of the threads of the bolt, causing a wedging action between them.

This makes the lower nut act as a lock nut. Theoretically, the lower nut, which is a lock nut, may be the thin nut, as shown in Fig. But as it required a special thin spanner to turn it, in practice, it is more usual to place the taking nut below the lock nut as shown in Fig. such cases sometimes two nuts of equal thickness are used as shown in Fig.

#7 Locking By Spring Washer

In this method of locking a coiled spring, the washer is placed underneath the nut, as shown in Fig. when the nut is tightened, the spring force of the spring exerts an axial force on the underside of the nut and holds it by the friction grip. This prevents the slackening of the nut.

locking by spring washer

A single coiled spring washer will be sufficient for light classes of work. When the vibrations are high, either a double-coiled or triple-coiled spring washer is used.

#8 Screw Pin Locking

A nut may be locked by a screw pin, screwed in the bearing surface adjoining the nut touching one of the lateral faces of the nuts, as shown in Fig. This type of locking is employed when the nut is expected to remain without any adjustment for a long time.

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All images are from Indiamart.com

About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

26 thoughts on “List of 20 Different Types of Nuts and Bolts [with PDF]”

  1. Thank you so much. I’m a single mom trying to put a table together. The table didn’t come with any nuts to fasten the bolts. I knew nothing about the world of nuts and bolts or much of anything mechanical!
    Appreciate your simple explanations!

  2. Hlo sir
    It’s Ashish here, I found your website today through YouTube and it’s so helpful for us. Basically I’m a student from ITI who is preparing for isro examinations but somehow the content you’re providing in mechanical engineering section is related to our iti syllabus and the thing i liked most that you’re explaining the terms in easy langauge with real figure which makes it more easy to understand. I’ll recommend this website to my frnds. Thanks a lot for such great help.

  3. Hi There,
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  4. It’s been nice and wonderful all through, I give my thumbs up for the engineer.however I would have loved to know more about how to get the formulae to calculate bolts and nuts and the equivalent wrench/spanner to be used as a mechanical engineer.


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