Torsion springs, whose ends are rotated in an 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. They 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 coils to minimize friction.

Double torsion springs can 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.