A Coil spring, also known as a helical spring, is a mechanical device, which 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 which returns to its natural length when unloaded.

Coil springs are a special type of torsion spring, the material of the spring acts in torsion when the spring is compressed or extended.

The two usual types of coil spring are:

• Tension coil springs which are designed to resist stretching. They usually have a hook or eye form at each end for attachement.

• Compression coil springs are designed to resist being compressed. A typical use for compression coil springs is in car suspension systems.

Metal coil springs are made by winding a wire around a shaped former - a cylinder is used to form cylindrical coil springs.

Springs (mechanical)