The materials are rubbed & dragged and the water flowed in the opposite direction inside of curved body which is made in the shape of a channel through the rotation of rubber covered shaft. The thin mud floating in the water is precipitated in the pool on the either side of this channel and the through the dirty water lost material are minimized. Screw washers are produced as single and double helical shafts are widely used machines to wash the materials between 0-10mm sizes.
