TourTour SHAFT Keys and Keyways
 Shaft diameter d mm
 Shaft torque T Nm
 Key length L mm
 key width b mm
 key height h mm
 keyway depth shaft t1 mm
 keyway depth hub t2 mm
 shear force Fs = T/(d/2) kN
 shear stress key τ = Fs /(Lb) MPa
 bearing pressure p = Fs /(h/2L) MPa
 Nominal torsional stress τ = T/(π/16dk3), dk=d-t1 MPa
Key dimensions: Parallel keys are most commonly used. The key and key seat cross section are ISO standardized. The key length should be less than about 1.5 times the shaft diameter to ensure a good load distribution over the entire key length when the shaft becomes twisted when loaded in torsion.

Stresses: Since compressive stresses do not cause fatigue failure, the bearing pressure is limited by the material yield strength YS of the weakest part, commonly the hub. The maximum shear stress in the key and the maximum torsional shear stress in the shaft can be derived from the yield strength of the shaft material.

Fatigue strength: Calculator for fatigue strength >>