Unlike a coil spring where the loops gradually go upwards, creating a spring that exerts vertical force; the loops of a spiral spring are all flat and wrap around each other, generating horizontal force when they are compressed.
A spiral spring usually has a hook or screw hole on the end that extends away from the spiral. This point is used to attach the spring to whatever component it will be functioning with. The center of the spiral will also usually have a hooked shape that can be fixed to a component that holds it in place when the spring is activated.
Spiral springs – also referred to as spiral torsion springs – are used in brush motors or other applications where a short rotation is required. Typically, the rotation from a spiral spring is only 360 degrees or less. Industries from automotive to healthcare to construction make use of spiral springs in a variety of tools and devices.
Spiral springs are useful when you need to allow for a slight rotation when force is exerted, but you want whatever device you are using to return to its natural position as soon as the force is removed. A good example of this is a drill press.
When someone turns a drill press on and then uses the handle to push the drill down, an internal spiral spring is compressed. As soon as the person operating the press lets go of that handle, the spiral spring returns to its original shape, causing the drill to pull up and out of the material it was drilling in to.
Manufacturing of spiral springs can be done using either a hot or cold machining process. In the hot machining process, metals are heated and then formed into a spiral using a mold that matches the desired specifications. In the cold machining process, the metal is cut into a long strip and then carefully pressed in circles around a center piece that supports it and helps it to retain its shape while being bent.
Steel and aluminum are common materials used to make spiral springs, but in applications where the spring may be required to conduct an electrical current, copper is used due to its low resistance to electricity.