1. Pressure plate :-

High tensile grey iron is the most commonly used material for pressure plate, which must be sufficiently rigid so as not to distort under the pressure of the clutch springs. Adequate rigidity is also needed to provide uniform pressure to clutch plate. The pressure plate should also have sufficient mass and thermal conductivity to absorb and conduct away the heat generated during engagement.

On the back of the pressure plate are cast a number of lugs to locate and support the release Lever and strut assemblies.

2. Reverse levers :-

The pressure plate in case of coil spring type clutch has a number of release levers, usually three or four, specially spaced around the pressure plate.

3. Cover :-

This is steel pressing bolted onto the flywheel and houses the pressure plate assembly. It provides pivot for the release levers and takes the reaction of the springs, due to which reason it must be sufficiently rigid. It should also have holes for the dissipation of heat.

4. Straps :-

A number of steel straps, usually four are arranged around the pressure plate. These straps hold together the cover and the pressure plate as one end of each strap is bolted to the pressure plate while the other end is connected to the cover. When the engine is running and the clutch is engaged, these straps deflect without affecting adversely the concentricity of the cover and the pressure plate and thereby transmit the drive from the cover to the pressure plate without any friction between them.

5. Springs :-

Normal duty clutch springs are made from oil tempered spring steel wire. However, for severe conditions they are made from silico-chrome steel to prevent heat set. Insulating washers are also sometimes used under extreme conditions to reduce heat conduction from the pressure plate to the spring.

The stiffness of the clutch spring should be maximum possible so that sufficient spring force is left after their extinction due to wear of the clutch facing. If the spring stiffness is excessively high, either excessive release pressure will be required when the clutch plate is new or else insufficient spring pressure will be available when the clutch facing has worn out. Usually, a 10 to 15% pressure variation is acceptable between the new and worn positions of the clutch facings.

6. Throwout bearing :-

It is used to transfer force at the pedal from the stationary linkage to the rotating clutch. This is either a thrust ball bearing which is packed with grease for lubrication, or else a graphite impregnated one fitted in a steel carrier. This later type, obviously does not require any lubrication.