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
D (wire diameter):
This parameter describes the diameter of wire used as material for spring.
De (External Diameter):
External diameter at large end of the spring. Tolerance for this parameter is (+-)2%(indicative).
Ds (Internal Diameter):
Internal diameter at small end of the spring. Tolerance for this parameter is (+-)2%(indicative)