Types of Fasteners [with Pictures]

What is Fasteners?

Types of Fasteners [with Pictures] :- Fasteners are the mechanical units which are used to join two or more objects together. Fasteners can be used to join either permanently or temporarily depending upon the site condition. There are numerous types of fasteners with different applications, about which one should definitely know.

Fasteners are categorized as Permanent or temporary units.

Example for permanent fasteners can be rivets, nails etc. which are single-use fasteners designed to join two objects permanently. Thus, these fasteners once installed cannot be removed, removing it can lead to destroy it. Whereas, temporary fasteners are designed to join two or more objects temporarily and can be removed and reused easily.

Example of temporary fasteners are bolts and screws which are commonly used in a number of industries and products as they allow the parts to re-assemble whenever required. Temporary fasteners are also known as threaded or non-threaded.

Types of Fasteners

Threaded Fasteners
Nuts
Washers
Rivets

A) Threaded Fasteners: ( Types of Fasteners )

These are the most commonly used fasteners mostly for assembling components which can be installed or removed as per the need. There are three most commonly used threaded fasteners i.e. Bolts, Screws and Studs. Let understand each of them in detail.

1. Bolts: ( Types of Fasteners )

Bolts are the ones which has a head on its one end, usually the hex head and are threaded on the other. These are usually used in combination with a nut or a washer to hold the material in the exact place.

2. Screws: ( Types of Fasteners )

Screws are quite similar to the bolts which also has a head on one end and a thread on the other head. They main difference is that screws are used to screw into a threaded hole. There are various types of screws which can be used according to the site requirement, like cap screws, machine screws, wood screws etc.

3. Studs: ( Types of Fasteners )

Studs are different from bolts and screws as they are threaded on the both ends, and thus do not have any head. This component is used to compile internally threaded holes together.

Types of Threaded Fasteners

1. Bolts and Set Screws

Bolts and Set screws are usually found having a hexagonal head accompanied with a thread which can easily be used in conjunction with a nut or a threaded hole. Bolts are generally found having a shank beneath the head, whereas set screws are threaded till the head.

2. Carriage Bolts

Carriage bolts are also known as cup square hex bolts which have a smooth rounded head and a square beneath. These fasteners are usually used to hold metal to wood.

3. Eye Bolts

Eye bolts have a circular ring instead of a traditional head and are used to fix chain to any surface.

4. U-Bolts

U bolts are used for upholding round objects such as pipes, tubes to the wall or any other surface.

5. Wood Screws

Wood screws are used in wood and come in various head shapes which can be selected according to the requirement.

6. Machine Screws

Machine Screws are accompanied with a nut or tapped hole.

7. Self-Tapping Screws

Also known as self-tappers, these screws are mostly used in metal sheets.

8. Socket Screws

Socket screws feature a smooth shank and has an Allen head which are fastened using an Allen key only. Socket screws are available in a different head shape like button, socket cap and counter sunk.

9. Grub Screws

Grub screws are a special type of screw which are found to have no head. These screws are used at the places where there needs to be no movement or rotation between two parts.

B) Nuts: ( Types of Fasteners )

Nuts are used with a bolt to join two or more mechanical parts together. The most commonly known nut is a hexagonal nut, but there are various other types of nuts which are used according to the site requirement.

1. Hex Nuts

Hexagonal nuts have an internal thread in them. These are the most common type of nuts, and are used in almost all types of industries with various applications.

2. Lock Nuts

Lock nuts are used to lock the nut in place without clamping any another object.

3. Nylon Insert Nuts

Well known as Nylon nut, these nuts have a nylon insert which does not let the nut loose due to the effect of vibration.

4. Shear Nuts

Shear nuts have a hexagonal gripping point which snaps off during the maximum torque, leaving just the nut which is quite difficult to remove.

5. Wing Nuts

Wing nuts are commonly used in applications where the nut needs to be removed frequently. These nuts have two external “wings shaped face” which allows for easy manual turning.

C) Washers: ( Types of Fasteners )

Washers are the units which are commonly used between the head of a bolt, screw, nut and any material which is being clamped. The main function of a washer is to increase the bearing area of the head and meanwhile also protect the material from any sort of damage. There are numerous types of Washers, with different uses and functions.

1. Flat Washers

Flat washers are the most common type of washers which are used to evenly distribute the load of the bolt, screw or nut.

2. Spring Washers

Spring Washers - Fasteners — Spring Washers

Spring washers or locking washers are designed to resist the bolt, screw or nut from losing with the effect of vibration.

3. Cup Washers

Cup Washers are mostly used in conjunction with a wood screw depending upon the requirement of the site.

4. Repair Washers

Repair Washers - Fasteners — Repair Washers

Commonly known as Penny or Fender Washers. These washers have a small diameter hole and are designed to create a greater bearing surface in order to prevent pull-through.

D) Rivets: ( Types of Fasteners )

Rivets are categorized in permanent fasteners, which once installed cannot be removed or reused. Rivets are used in various industries to fulfil various applications but are most commonly used to join metal sheets and plates.

1. Pop Rivets

Pop rivets consists of a hat and a mandrel. These rivets are used to join two mechanical materials together during installation.

2. Large Flange Pop Rivets

Large Flange Pop Rivets - Fasteners — Large Flange Pop Rivets

Large Flange Pop Rivets are very similar to Pop Rivets in their applications but offers various features as compared to Pop rivets.

3. Multi-Grip Rivets

Multi Grip Rivets - Fasteners — Multi Grip Rivets

Multi grip rivets are used to join materials with varying thickness, which would normally require various rivet sizes. These rivets are found to be versatile and cost-effective.

Rivets – Types, Failures Of Riveted Joint, Terms Used In Riveting

Rivets are short ductile and cylindrical bars that are used for making a permanent mechanical joint.

The process of forming a riveted joint is called riveting.

A rivet is divided into 3 parts i.e., the head at one end, the tapered tail, and shank, the portion between the head and tail as shown in the figure.

As it is a permanent joint it cannot be disassembled without the failure of the machine component.

The material of rivet should be tough and ductile.

They are usually made of low carbon steel, nickel steel, Brass, Aluminum, copper, etc.

Physics Behind Rivetting

The main function of a rivet is to make a connection, that has the strength to prevent failure and tightness to prevent leakage.

For connecting “> 2 metal plates, firstly holes are punched and reamed. The plates are then separated to remove any burrs or chips.

The cylindrical cold or red-hot rivet is then inserted into the hole.

Then the head is backed by a hammer or heavy bar and then the die as shown in the figure and is placed against the end to be headed, and the blows are applied by a hammer.

Force applied causes the shank to expand and fill the gap. The force applied deforms the tail plastically and forms the required shape.

As the rivet cools down, it contracts. But the lateral contraction is slight and there will be longitudinal tension which holds the plates firmly together.

**The cold riveting process is used for structural joints while hot riveting is used to make leak-proof joints.**

TYPES OF RIVET HEADS

Rivethead is classified into 3 broad categories:

For the general-purpose that is below 12mm diameter

General purpose between 12-48 mm diameter

Boiler work between 12-48 mm diameter

The snap head rivets are usually employed for structural work and machine riveting. The countersunk heads are used in shipbuilding where the flush surface is required. The conical or conoidal head is mainly used in the case of hand hammering. Pan heads have the maximum strength but are difficult to shape.

TYPE OF RIVET JOINTS

Rivet joint is classified into 2 types depending on the way in
Which the plates are connected.

Lap joint:

A lap joint is one in which one plate overlaps the other,
And the two plates are then riveted together.

Butt-joint:

A butt joint is that in which the main plates are Kept in alignment with each other and a cover plate (called strap) it is placed either on one side or on both sides of the main plates.

The cover plate is then riveted together with the main plates.

The butt joint is further dived in 2 types:

Single strap butt joint
Double strap butt joint

In a single strap butt joint, The edges of the main plates are placed against each other and only one cover plate is placed on one side of the main plates and then riveted together.

In a double strap butt joint, the edges of the main plates are placed against each other and two cover plates are placed on both sides of the main plates and then riveted together.

In addition to above, depending on the number of rows of the rivets They are classified as single riveted joint, Double riveted, triple, quadruple and chain riveted joints.

TERMS USED IN RIVETED JOINTS

Pitch: It is the distance from the centre of one rivet to the centre of the next rivet measured parallel to the seam. It is usually denoted by p.
Back pitch: It is the perpendicular distance between the centre lines of the successive rows. It is usually denoted by PB.
Diagonal pitch: It is the distance between the centers of the rivets in adjacent rows of zigzag riveted joints. It is usually denoted by PB.
Margin or marginal pitch: It is the distance between the centres of rivet hole to the nearest edge of the plate. It is denoted by m.

FAILURES OF RIVETED JOINT

Riveted joint may fail in various ways:

Tearing of plate at an edge

A joint may fail due to the tearing of the plate at an edge.
And this can be avoided by keeping the margin, m = 1.5d,
Where d is the diameter of the rivet hole.

Tearing of plate across the rows of rivets

Due to the tensile stresses in the main plates,
The main plate or cover plates may tear off across a row of rivets.
In such cases, we consider only one pitch length of the plate,
Since every rivet is responsible for that much length of the plate only.

Shearing of rivets

The plates which are connected by the rivets exert tensile stress on the rivets, and when the rivets are unable to resist the stress, they shear off.

Crushing of rivets

Sometimes, the rivets do not shear off under the tensile stress, But are crushed.

Due to this, the rivet hole becomes oval and hence the joint becomes loose.

Sunday, June 6, 2021

TYPES OF FASTNERS