What is Mechanical Pin?: Classifications, Types, Uses with Pictures

We know that a “machine is a device used to convert available energy into useful work”. There are so many parts in a machine between the source of energy and work to be done which converts energy into work.

A machine is composed of several parts and components. Parts and components are assembled help of pins and cotters. knuckle joints, gears, splines, keys, keyways, shafts, collars, cranks, eccentrics, couplings and clutches, bearings, springs, belts, ropes, pulleys, chains and sprockets, etc.

Today, I am going to discuss Mechanical Pin or fastening pins or pin fasteners with classification, types, Uses and much more. So, Stay with me and scroll gently to get most of the juice from this article.

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What is Mechanical Pin?

Fastener Pins are made in cylindrical and tapered shapes. Generally, it is made of mild steel rods. They are hardened and ground as required.

It is a temporary fastening device. The parts to be joined are drilled in proper sizes and pins are inserted in them to form a temporary joint. It is easy to prepare joints with pins in comparison to other fasteners.

Classification of Pins-

On the basis of the nature of the joint to be made by the pin, pins may be classified as:

  1. Quick-release pin fasteners
  2. Semi-permanent pin fasteners

1. Quick-release pin fasteners-

It is also known as the “Tee-Handle Pin fastener”. These pins are easy to insert in a hole and removed from it Their fitting is loose in the hole.

For example- bar clamp.

quick release pin

2. Semi-Permanent pin fasteners-

The joints, made of semi-permanent pins, cannot be opened easily. They are assembled and opened by hammering, Such joints are known as semi-permanent joints and make use of “semi-permanent pin fasteners”.

They can be further divided into two categories:

  1. Radial Locking Pins
  2. Machine Pins

They are briefly detailed below:

I. Radial locking Pin-

These pins rigidly hold the joint. They are used for such joints which are subject to vibration loads and impact loads. They have special shapes.

These pins are rigidly fixed on the periphery of the hole because of their special shapes. They are cheap and easy to use.

The radial locking pin can be categorised in the following two ways:

  1. Grooved Pins or Slotted pins
  2. Spring Pins
A. Grooved Pins-

Grooved or slotted pins have slots cut on them at equal intervals on their periphery longitudinally. When this pin is inserted and hammered into the hole, elastic deformation takes place and it takes a strong grip on the periphery of the hole.

B. Spring Pins-

Spring pins are radially compressed when inserted and hammered in the hole, providing rigidity.

II. Machine Pin-

Machine pins are basically used to join two components to each other and it usually employed in industrial applications.

There are various types of machine pins according to shapes and needs and they are-

  1. Dowel Pins
  2. Taper Pins
  3. Clevis Pins.
  4. Cotter or Split Pins
  5. Safety Pin

These are described in brief:

I. Dowel Pin-

These pins are cylindrical in shape. They are hardened and ground. When two parts are to be joined, pins are used for their accurate alignment and to keep their relative positions.

They are available in standard sizes.

dowel pin

II. Tapper Pin-

These pins have a standard taper in the body, One end is large and the other small. The small end is inserted in the reamed hole and pressed by hammering.

These pins are used on shafts. hubs etc, to fit wheels and levers. In a blind hole, the pin is fixed with the help of a nut. The crank and axle of the bicycle are connected with this type of pin.

taper pin

III. Clevis Pin-

 It is a cylindrical pin with a head on one end and a radially drilled hole on the other end. After inserting this pin in the hole a split pin is fixed in the radial hole which locks the pin in a fixed position.

For example, a rod fixed in the hook of a ceiling fan carries the split pin. These pins are used to make suspension links and knuckle joints.

clevis pin

IV. Cotter Pin-

They are made from wires of the semi-car section, joined together in such a way as to form a circular section of the required length. The quality steel is in standard sizes.

After inserting the pie the projecting length of the cylindrical part is opened into two halves by a plier or long and best in opposite directions.

When used in belt-joint a hole drilled radially in the build equal to the size of the pin. For other fasteners, these pine act as the locking device.

When the pin has to be taken out, its legs are straightened and the other end is pulled by the plier. In a good joint, the pin should be assembled in such a way that its head should not project out and it should be level with the part in which it is used.

cotter pin

V. Safety Pin-

When a pin is used for the safety of a part, it is called the safety pin. When an operation is subjected to overload, the pin fails, but the part is not spoiled.

safety pin

Important joints made by the use of machine pins:

Two prominent joints using machine pins are:

  1. Knuckle Joint
  2. Suspension Link

A. Knuckle Joint-

 It is also called a pin joint. This joint is used for transmitting power in an angular direction, joining two shafts, joining piston rod and connecting rod and converting reciprocating motion into rotary motion.

Apart from this, it is also used in links of bicycle chains, to join tensile members of roof trusses, tensile links of bridges, joints of pump rods, various joints of levers and rods etc.

A knuckle joint is used to make a temporary joint on the two shafts to be joined axially which have to transmit tensile load.

If guides are used with this joint, it can be used to transmit compressive load. The advantage of this joint is that it can be easily opened and assembled for adjustments and repairs.

To construct a knuckle joint, the end of a rod is forged by upsetting and machined to form an eye. Similarly, the shape of a fork is made on the end of another shaft.

The fork is also machined to form an eye on both parts. Now in between the two machined parts of the fork, the shaft with one eye is inserted in such a way that all three eye holes coincide with each other.

Now the knuckle pin is inserted through the eye holes and the collar is set to fit a cotter pin or split pin through it. The parts of this joint are made of mild steel or wrought iron.

knuckle joint

B. Suspension Link-

A suspension link consists of two thin links connected to a thick link by means of a pin passing through them and locked by a cotter pin or split pin at one end.

The ends of suspension bridge links are generally wider. Suspension links are used to support machine devices and suspension bridges.


Wrapping Up- 

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