Drive shaft fatigue strength with a keyway
Standard key cross-section for a given shaft diameter, and the fatigue strength (static and cyclic torque limit) of the shaft at the keyway root.
Key width, b6 mm
Key height, h6 mm
Keyway depth, shaft, t₁3.5 mm
Keyway depth, hub, t₂2.8 mm
Critical diameter, d_k = d − t₁16.5 mm
Section modulus for torsion, S = I_p/(d_k/2) = (π/16)d_k³0.88 10⁻⁶ m³
Maximum shaft torque, statically loaded, T = S·τ441.01 Nm
Maximum shaft torque, cyclically loaded, T = S·τₑ/Kₜ124.04 Nm
Method & references
- Fatigue strength of a drive shaft with a keyway, at the keyway-root critical diameter.
The computation is a literal port of the original client-side JavaScript from /calculators/key_d.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.