Helical Compression Spring

Spring rate and Wahl-corrected shear stress of a round-wire helical compression spring — for design or checking a stock spring.

SpringWahlEN 13906

Spring rate k4.84N/mm

METHOD

How it is calculated

k = G·d⁴ / (8·D³·N_a)
C = D / d      K_w = (4C − 1) / (4C − 4) + 0.615 / C
τ = K_w · 8·F·D / (π·d³)

ASSUMPTIONS & NOTES

G = 79.3 GPa applies to spring steel (e.g. EN 10270-1); stainless spring wire ≈ 69 GPa.
Allowable shear stress depends on wire size and material (EN 13906-1).
Check long springs for buckling (L₀/D ratio).

Results are for preliminary design and checking; base the final design on the governing standard and safety factors.

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