A clutch is a device which provides a means of controlling or interrupting the drive or transmission of rotary motion between two shafts.

Various types exist, the more common designs are centrifugal clutch, electromagnetic clutch and friction clutch.

A centrifugal clutch relies on an increase in rotational speed acting upon moving parts within the unit to move outwards due to the increasing centrifugal force whereupon they engage with an adjacent part within the clutch and cause drive to be transmitted through the clutch.

An electromagnetic clutch works upon the principle of switchable electro-magnetic attraction between elements within the clutch allowing it to engage and disengage using a controlled power supply.

A friction clutch utilises a plate onto which are secured thin pads or discs made from a high frictional coefficient material. This frictional face is moved up to and away from the driving plate to engage or disengage drive. Friction linings wear out especially when transmission take up loads are excessive or inefficient. Excess wear can result in clutch or drive slippage before leading to loss of drive altogether.

Selection criteria to be considered are, speed, torque, power, application, alignment and service factor.

Accurate and clean setup is critical for a long service life and mating parts must fit precisely.

Typical clutch mounting/drive arrangements include splined profile shaft or parallel key driven shaft.

A typical example of a clutch is shown on the picture..