Drawing No. EH–ME–007 // Mechanical Engineering
Keyway & Fastener Calculator
Reviewed August 2026
Two practical screening tools: parallel-key shear/bearing capacity and direct-load fastener tension/shear yielding.
Calculation workflow
Inputs are converted internally to SI, the engineering model is solved, and results are converted back to the selected unit system.
Keyway inputs
Keyway results
Fastener inputs
Fastener results
Background
Keys transmit shaft torque by tangential force; fasteners may carry simultaneous direct tension and shear.
F = 2T/d; τ = F/(bL); σbearing = F/(0.5hL)
The bearing model assumes half of the key height carries compressive load.
σvm = √(σ² + 3τ²)
This is a material-yield screening check for direct loads only. It does not replace a complete bolted-joint analysis.
Frequently asked questions
Practical questions about assumptions, limits and interpretation.
The calculator assumes the transmitted tangential force acts over one-half of the key height, giving bearing stress approximately 4T/(d h L).
No. Shaft and hub keyways create stress concentrations that can govern fatigue strength even when the key itself passes shear and bearing checks.
The fastener tab assumes the entered total direct tension and direct shear are shared equally by the entered number of fasteners. Eccentric load, prying and joint stiffness are not included.
Tension should normally use an appropriate threaded tensile-stress area. For shear, select whether the shear plane passes through an unthreaded shank or use the entered stress area as a conservative threaded-plane approximation.