Torsion Spring Design

Torsion springs exert a torque when they are twisted or deflected. The spring torque and the length of the legs together create a force. Torsion springs can be made out of round, rectangular or shaped wire.
A simple torsion spring has straight, but any bends or shapes can be formed. Double torsion springs can
be used when twice the force is required or when you need an even distribution of torque.
For more information on Torsion springs , contact Katy Spring today at 281-391-1888

Double Body Torsion Spring

.080 Brass Double Body Torsion Spring

Torsion Spring

Torsion Spring

Common Spring materials:

TTorMaterial Max. recommended % tensile in bending
Music Wire 80%
Chrome Silicon 80%
Chrome Vanadium 80%
302 Stainless Steel 60%
316 Stainless Steel 60%
17-7 Stainless 75%

Spring Terms
ID = Inside Diameter
D = Mean Diameter
Dm = Minimum Diameter under deflection
 = Deflection angle
d = wire diameter
L = leg length
Na= number of active coils
Nt = number of total coils
R= Spring Rate
P = applied force
M = Moment or Torque
Sb = bending stress
c = spring index
?L = deflection
UTS= Ultimate Tensile Strength
Design Tips
• Torsion springs should be deflected in
the direction that closes the coils
• Inside diameters reduce to Dm when
deflected. Mandrel size should be
larger than Dm
• Na takes into account the material in the
legs. If the force is supplied close to the
body of the spring Nt is a good