How to use this calculator
- Enter wire and coil geometry. Enter music wire diameter, mean coil diameter and active coils.
- Enter free length and deflection. Free length sets travel to solid, while deflection sets the working load point.
- Choose end type. End type changes inactive coils and solid height.
- Read rate and force. The calculator returns spring rate and force at the entered deflection.
- Check stress. Compare Wahl-corrected stress with the music-wire allowable at that wire size.
How it works
Music wire uses the same helical compression spring equations as other round-wire
springs. The rate is:
k = G*d^4/(8*D^3*Na)
where G = 79.3 GPa for ASTM A228 music wire.
The working load is F = k*x. Stress is corrected for coil curvature
with the Wahl factor:
Kw = (4C - 1)/(4C - 4) + 0.615/C, where C = D/d.
The corrected stress is tau = Kw*8*F*D/(pi*d^3).
Music wire tensile strength depends on wire diameter, so the calculator estimates
Sut(d) at your entered wire size and uses 0.45*Sut as
a static allowable shear stress.
Worked example
Verified against the live calculator
With d = 1.0 mm, D = 10 mm, Na = 8 and
10 mm deflection, music wire gives k = 1.239 N/mm and
F = 12.39 N.
The spring index is C = 10, the Wahl factor is 1.1448,
and corrected stress is about 361 MPa. Estimated music-wire tensile
strength at 1 mm is 2,211 MPa, so the static allowable is
995 MPa.
Spring material data
Music wire is a high-strength carbon spring wire. The values below are typical design inputs; verify against the supplier certificate and governing standard for production work.
| Property | Value |
|---|---|
| Specification | ASTM A228 |
| Shear modulus G | 79.3 GPa / 11.5 Mpsi |
| Young modulus E | 207 GPa / 30 Mpsi |
| Static design stress | 45% of Sut |
| Typical max service temperature | 250°F / 121°C |
Source: ASTM A228 music-wire property references and published spring-design data. Verify supplier-certified values for production design.
Frequently asked questions
What is music wire?
Music wire is high-strength, cold-drawn carbon spring wire commonly specified as ASTM A228. It is widely used for small compression, extension and torsion springs.
How do you calculate music wire spring rate?
Use the standard helical spring rate formula k = G*d^4/(8*D^3*Na). For music wire this calculator uses G = 79.3 GPa (11.5 Mpsi).
How do you calculate music wire spring stress?
The corrected compression-spring stress is tau = Kw*8*F*D/(pi*d^3), where Kw is the Wahl correction factor and F is the working load.
What allowable stress does this use?
For a static first-pass check, this calculator uses 45% of the estimated minimum tensile strength at the entered wire diameter. Fatigue designs need a separate stress-range check.
What temperature can music wire handle?
Music wire is commonly limited to about 250°F / 121°C service temperature. Stainless, chrome-silicon or other alloys may be better for heat or corrosion.
Is this different from the compression spring calculator?
The formulas are the same, but this page fixes the material to ASTM A228 music wire and exposes the music-wire tensile strength and allowable stress directly.
Method & assumptions
- Material is fixed to ASTM A228 music wire.
- Static loading only; fatigue and stress relaxation are not modeled.
- Allowable shear stress is estimated from size-dependent tensile strength.
- Temperature, corrosion, set removal, shot peening and supplier tolerances require separate review.