Coil spring

A coil spring is a mechanical device that is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces.

They are made of an elastic material formed into the shape of a helix that returns to its natural length when unloaded.

Under tension or compression, the material (wire) of a coil spring undergoes torsion.

The material of the spring is thereby subjected to a bending moment, either reducing or increasing the helical radius.

A machine called an auto-coiler takes spring wire that has been heated so it can easily be shaped.

It is then fed onto a lathe that has a metal rod with the desired coil spring size.