Spiral Springs, also known as spiral-torsion springs, are made of rectangular-section, annealed (soft) spring steel. Once properly formed, the custom spiral springs are then heat-treated to achieve their proper spring function. Like wire torsion springs, spiral springs produce a linear torque. In most cases, spiral springs are best suited for applications requiring less that 360 degrees of angular rotation. However, properly designed custom spiral springs may exceed that limit provided that there is no coil binding, which would cause an unwanted spike in torque and stress.
A delicate spiral torsion spring is used in watches, galvanometers, and places where electricity must be carried to partially rotating devices such as steering wheels without hindering the rotation.