Shaft Diameter
Minimum diameter of a solid shaft carrying both bending and torsion, using the ASME shaft design equation (maximum shear stress theory). The result is rounded up to the next standard shaft size.
Minimum shaft diameter d37.8mm
- Equivalent torque T_e
- 424.3 N·m
- Suggested standard diameter
- 38 mm
- Shear stress at standard size
- 39.4 MPa
- Key for this size (DIN 6885)
- 10 × 8 mm
- With a keyway, reduce τ_allow by 25 % (ASME)
METHOD
How it is calculated
T_e = √((K_m·M)² + (K_t·T)²) d = ∛(16 · T_e / (π · τ_allow))
ASSUMPTIONS & NOTES
- Shock factors: steady load K_m = 1.5, K_t = 1.0; minor shock K_m = 1.5–2.0, K_t = 1.0–1.5; heavy shock K_m = 2.0–3.0, K_t = 1.5–3.0.
- ASME recommends τ_allow = the lesser of 30 % of yield or 18 % of ultimate strength, reduced by 25 % at a keyway.
- Fatigue and torsional stiffness (angle of twist) must be checked separately.
Results are for preliminary design and checking; base the final design on the governing standard and safety factors.
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