To obtain fine material both of the rolls should be chosen as smooth faced. For intermediate sizes one of the roll should be corrugated type. Both of the rolls should be chosen as corrugated in order to crush coarse material. The roll crushers are equipped with hydra-pneumatic system against the iron pieces in the feeding material. It is also easier to adjust the discharge opening by the help of this system. Drive system consists of pulley and V-belt for the first steep. The second step is driven by oil lubricated closed spur gears. The power is transmitted from one roll to another by wheel tires. The flywheel shaft and the roll shafts are product of C45 carbon steel. They are mounted with heavy duty spherical roll bearings and sealed with the labyrinth type of seals.