KEVOS® MAKEOS · Springs
Square versus Round Wire Spring Comparison (Rate, Load, Stress, Solid Length)
In the same space, would a square-wire or a round-wire compression spring of the same size give me the load I need within stress?
Side-by-side check of two compression springs with the same coil diameter, active coils, free and working lengths: one wound from square wire of side a (as the square-wire spring tool) and one from round wire of diameter a (as the compression spring tool) — rate, load at the working length, corrected stress, solid length — and which of them gives the load you need within the allowable stress.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Wire size (square side or round diameter) | mm | Side of the square wire, and diameter of the round wire compared with it. |
| Mean coil diameter | mm | Mean coil diameter of both springs. |
| Active coils | coils | Active coils of both springs. |
| Shear modulus | GPa | Shear modulus of the wire. |
| Unloaded length | mm | Unloaded length of both springs. |
| Working length | mm | Length both are compressed to. |
| Allowable shear stress | MPa | Allowable corrected shear stress. |
| Load needed at the working length | N | Load the spring must give at the working length. |
Method and formulas
- Square wire: k = G a⁴ ÷ (5.58 N_a D³); stress = 0.96 K F D ÷ (0.416 a³) (as the square-wire spring tool).
- Round wire: k = G d⁴ ÷ (8 D³ N_a); stress = K 8 F D ÷ π d³ with the Wahl factor (as the compression spring tool).
- Solid length = (active coils + 2) × wire size for closed and ground ends.
- Example: square wire gives 269.8 N at 564.77 MPa; round wire 188.18 N at 434.69 MPa.
Limitations
- Square wire assumed to stay square in the coil; in practice it becomes keystone-shaped.
- Static load; closed and ground ends for solid length.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Decide whether square wire gives enough extra load
- Compare die spring options in a fixed pocket
- Check solid length for both wire shapes
Who it is for
- Design engineers
- Toolmakers
- Spring buyers
What you get
- Rate and load of each spring
- Corrected stress of each
- Solid length and which meets the need
Interpreting the result
- Square wire stores more energy in the same space, but costs more and is harder to obtain.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 304–324. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Square versus Round Wire Spring Comparison (Rate, Load, Stress, Solid Length) calculator
