A Torsion Spring has ends are rotated in angular deflection and 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. A Torsion Spring of this type is usually close wound, reduced in coil diameter, and increased in body length as they are deflected. The designer must consider the effects of friction and arm deflection on the torque.

A Torsion Spring can include a double Torsion Spring and have a space between the coils to minimize friction. A double Torsion Spring consists 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.