Extension springs which absorb and store energy by offering resistance to a pulling force. Various types of ends are used to attach the extension spring to the source of the force.

Torsion springs, whose ends are rotated in angular deflection, offer resistance to externally applied torque. The wire itself is subjected to bending stresses rather than torsional stresses, as might be expected from the name. Springs of this type are usually close wound, reduce in coil diameter, and increase in body length as they are deflected. The designer must consider the effects of friction and arm deflection on the torque.

Special types of torsion springs include double torsion springs and springs having a space between the coils to minimize friction. Double torsion springs consist of one right-hand and one left-hand coil section connected together, and working in parallel. The sections are designed separately with the total torque exerted being the sum of the two.

Flat Springs covers a wide range of springs and forms fabricated from flat strip material which, on being deflected by an external load, will store and then release energy. Flat springs and strip forms are designed to perform functions beyond normal spring functions, e.g. act as a latch, or hold a part in position.