A screw is a mechanical system that converts rotational motion in to linear motion. In other worlds it converts rotational force (torque ) in to a linear force. Here the resultant axial force due to an input torque is calculated from first principles.
Worm Drives are used when the axis of rotation of a shaft must change direction. Being low-cost, potentially self-locking and providing high gear reductions, Worm Drives provide an effective means of decreasing speed whilst increasing torque.
Mechanical screw jacks and linear actuators are increasingly becoming the preferred choice of actuation over the equivalent hydraulic or pneumatic systems.