Shaft Design Calculator
Design a shaft for combined bending and torsional loads using the von Mises failure criterion. Calculates minimum diameter and stresses.
Inputs
in·lb
in·lb
psi
Results
Minimum Shaft Diameter
1.44 in
Von Mises Stress
18,000 psi
Shear Stress (τ)8,542 psi
Bending Stress (σ)10,251 psi
Allowable Stress18,000 psi
How to Use This Calculator
- Enter the Applied Torque (T) in in·lb from power transmission — use T = 63,025 × HP / RPM if starting from motor horsepower.
- Enter the Bending Moment (M) in in·lb from transverse loads such as gear separating forces, belt tension, or overhanging weight.
- Enter the material Yield Strength (Sy) in psi: 1018 steel ≈ 36,000 psi, 4140 steel ≈ 60,000 psi.
- Set the Safety Factor: 2.0 for well-defined static loads, 2.5–3.0 for fatigue or shock loading.
- Read the Minimum Shaft Diameter in inches and round up to the next standard size for keyway compatibility.
- Review the Von Mises Stress versus the Allowable Stress to confirm the design margin is adequate.
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