Crushing plants are used to produce aggregates. The sizes of stones fed depend upon the capacity and crushing system adopted. The main types of crushers are: - Jaw crusher. - Impact crusher. - Roller crusher. - Cone crusher.

Jaw Crusher:

• Jaws crush the stones by compression. The jaw crushers are used as either primary or secondary crushers.

• These are suitable where lesser fines are desired.

• These crushers have two jaws i.e Fixed Jaw and Swing Jaw.

• The fixed jaws are made up of high manganese cast steel.

• The swing jaw are made of either manganese chrome or heavy duty cast steel.

• The capacity of crusher is influenced by the size of the product, nature and type of rock.

Impact Crusher:

• These crushers are used where materials are too hard and abrasive and finished product requirement is for cubical shape.

• The stones are broken by means of impact and not by compression as in jaw crusher.

• The stone is normally fed into top of a breaking chamber and struck by rotating hammers while it is in suspension.

• These crushers are used for primary or secondary crushing.

Cone crusher:

• These are used to produce the final product, since they can receive and crush smaller size of stones of ore and produce more fine aggregates.

• The stones are fed through feed chute, evenly into the crushing chamber where they are crushed quickly and uniformly.

• The crusher head has a gyratory, swinging motion so that crushing is done by direct pressure.

• This results in cubic product.

Gyratory Crusher:

• Like cone crushers, these also crush the rocks by applying pressure to the rock boulders between a stationary surface and rotating curved surface.

• The crushed materials are discharged by gravity.

• This crusher provides much larger crushing surface than jaw crusher.

• These are generally used for primary crushing because of larger eduction ratio.