Screw (simple machine)

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A screw is one of the six simple machines. A simple screw is a helical inclined plane. A screw can convert a rotational force (torque) to a linear force and vice versa. The ratio of threading determines the mechanical advantage of the machine. More threading increases the mechanical advantage. A rough comparison of mechanical advantage can be done by taking the circumference of the shaft of the screw and divide by the distance between the threads.

A screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. It can also be defined as an inclined plane wrapped around a shaft. Screws come in a variety of shapes and sizes for different purposes.

Mechanical Advantage

The mechanical advantage of a screw without using a screwdriver is:

P = Pitch of screw

C = Circumference of the head $MA = C / P$

The mechanical advantage of a screw using a screwdriver is:

P = Pitch of screw

C = Circumference of the screwdriver handle

$MA = C / P$

The distance between two corresponding points on adjacent threads is called the pitch.

Examples

Lead screw and ball screw are specialized screws for translating rotational to linear motion.
Automated garage door, where a motor drives a long finely threaded shaft at relatively high speed and lifts the heavy door at a slower rate.
Archimedes' screws and worm gears are examples of this machine.

Screw (simple machine)

Mechanical Advantage

Examples

See also