KEVOS® MAKEOS · Springs
Square-Wire Compression Spring
What rate, load and stress does this square-wire compression spring have?
Rate, load at working length and torsional stress of a helical compression spring wound from square wire, using the handbook’s square-wire constants.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Wire side | mm | Side of the square wire (radial and axial thickness). |
| Mean coil diameter | mm | Mean coil diameter. |
| Active coils | coils | Active coils. |
| Shear modulus | GPa | Shear modulus of the wire. |
| Unloaded (free) length | mm | Length with no load. |
| Working length | mm | Installed or working length. |
| Allowable shear stress | MPa | Allowable shear stress for the material and duty. |
Method and formulas
- Deflection F = 5.58 P N D³ ÷ (G a⁴), so rate = G a⁴ ÷ (5.58 N D³) (round wire uses 8 and d⁴).
- Uncorrected stress S = P D ÷ (0.416 a³).
- Corrected stress uses the Wahl factor reduced by about 4% for square wire.
- Example: 3 mm square wire at 20 mm mean diameter gives k = 17.986 N/mm and 269.8 N at 45 mm.
Limitations
- Square wire keystones (deforms) during coiling; the formulas assume a square section in the coil.
- Solid length and buckling as for round-wire springs.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check square-wire and die springs
- Compare square and round wire for the same space
- Specify a replacement spring
Who it is for
- Design engineers
- Spring buyers
- Toolmakers
What you get
- Spring rate
- Load at working length
- Corrected shear stress
- Spring index
Interpreting the result
- Square wire stores more energy than round wire in the same space but costs more.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 304–324. Topic reference; no source tables or recommended settings are reproduced.
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