When to use splines vs keys?

Splines for higher torque, self-centering, sliding connections. Keys for simpler, lower-cost applications.

What is the pressure angle effect?

30 degrees standard. Higher angles give stronger teeth but more radial force.

What load distribution factor?

K=0.75 for fixed splines, K=0.5 for sliding under load.

How long should engagement be?

0.75D to 1.25D pitch diameters.

What materials work best?

Case-hardened alloy steel 58-62 HRC for high loads.

Free Engineering Tool #075

Spline Connection Calculator — ISO 4156

ISO 4156 involute spline design. Enter module, number of teeth, pressure angle, engagement length, and torque to calculate load capacity and bearing stress.

ISO 4156Involute SplineAuto-Calc

Results

Torque Capacity

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Pitch Diameter

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Bearing Stress

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Safety Factor

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Root Diameter

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Pitch Diameter

Bearing Stress

where h = effective tooth height (approx 0.9m), z = teeth, L = engagement length, K = load distribution factor, Dp = pitch diameter.

Load distribution: K=0.75 fixed, K=0.5 sliding under load. This calculator uses K=0.75.

Spline Connection Calculator ISO 4156 | Free Tool #075

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Pitch Diameter

Bearing Stress