The screw conveyor is one of the oldest and most versatile conveyor types. These are compact, requiring little headroom and no return mechanism. The material is also mixed as it passes through the conveyor. Screw or helical flight conveyors consists of a steel shaft having a spiral or helical fin fastened to the shaft and rotating in a trough without touching the trough, so that the helical fin pushes the material along the trough. The shaft is driven by a motor coupled with a reduction gearbox.