Torsion springs and Extension Sprins are similar in appearance but different in shapes. The both ends of torsion springs are made into the long-arm shapes. Mostly direction of a force follows the direction of helix tangents, and it becomes so called “ torsion force”. The axis of a spring would generate a rebounded torsional moment after it deformed by a torsion force, and the machine part could return to the original action thus. Therefore, the mechanical function of parts could be controlled by using torsion springs.