A torsion spring is a mechanical element that controls and assists rotational movement by having arm sections, located at both ends of a coiled wire material, receive a load (torsional moment) perpendicular to the coiling direction. As the arms twist, energy is stored, and it acts as a restoring force. Its main applications are diverse, including assisting the opening and closing of hinge mechanisms, restoring levers, providing tactile feedback for switches, and clutch mechanisms. The manufacturing process involves forming wire materials such as piano wire, stainless steel wire, and oil-tempered wire into a coil shape using a wire forming machine, and bending the arm sections to a specified angle. In design, careful consideration of the arm shape, point of action, and stress concentration is crucial.