What is Key in Mechanical Engineering

In this article, we learn what is key in mechanical engineering and the types of key in mechanical engineering.

What is Key in Mechanical Engineering?

The key is a mechanical component made of mild steel that is inserted to prevent relative movement between the shaft and the hub (pulley boss, gear, sprocket).

The key transfers torque from the shaft to the hub or from the hub to the shaft.

This is always included in the provided key-way parallel to the axis of the shaft.

A key-way is a slot or recess in the shaft and hub of a rotating component (gear, pulley, crank) to insert a key.

Typically, a key is heavily crushed and sheared.

Types of Key in Mechanical Engineering

The following are the commonly used types of key in mechanical engineering.

types of key in mechanical engineering

1. Sunk Keys

The sunk keys are placed in such a way that half of it is on the key-way of the shaft and the other half is in the hub of the rotating element or key-way of the boss.

The types of sunk keys are as follows.

i) Rectangular key

ii) Square key

iii) Parallel key

iv) Gib-head key

v) of feathers

vi) Woodruff’s

iii) Parallel Key or Parallel Sunk Key

Parallel sunk keys may be rectangular or square cross-sections and they are taperless.

The below diagram is the parallel sunk key diagram.

Parallel Key

2. Saddle Keys

The saddle key is a tapered key that fits perfectly into the key-way supplied to the center of the rotating element.

This key has a low capacity to transmit torque. There are two types of saddle keys:

A.Flat Saddle Key

B. Hollow Saddle Key

3. Tangent Keys or Kennedy Keys

The tangent key or Kennedy key consists of two tapered rectangular or square keys perpendicular to each other. These keys are hard to fit.

Applications: These are used in heavy-duty application applications.

4. Round Keys

The Round keys are also called Pin keys which are rounded in cross-section.

Applications: These keys are used for low-power drives.

5. Splines

Splines are multiple keys that are made inseparable with shafts that fit in the key routes broached into the hub.

This type of shaft is called the splined shaft.

Applications: Splined shafts are commonly used in automobile and machine tool gearboxes.


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