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.
Bevel gears are used when the axis of rotation of a shaft must change direction. Providing a highly efficient and durable means of gear reduction, Bevel Gear sets have many uses.