Shaft Keyway Size Calculator

Shaft Keyway Size Calculator

Keyways (the slots cut into a shaft to hold a key, transmitting torque between shaft and hub) follow standardized dimension tables based on shaft diameter - this calculator looks up the appropriate standard sizing.

Example

A 25mm diameter shaft:

Recommended keyway: 8mm wide x 4.0mm deep

Why Standardized, Discrete Steps Instead of a Formula

Standard keyway dimensions scale in discrete steps with shaft diameter, following widely used engineering standards, rather than a smooth continuous formula - this ensures interchangeable keys and consistent fit across different manufacturers all building shafts and keys to the same standard diameter ranges, similar to how bolt sizes follow standardized increments rather than arbitrary continuous dimensions.

Metric vs. Imperial Standards

This reference table follows conventions similar to metric DIN 6885 standards - imperial ANSI B17.1 standards use a somewhat different sizing table for the same nominal shaft diameters expressed in inches. Always verify the exact specification standard that applies to your specific design and region before finalizing keyway dimensions, since mixing standards can result in incompatible key/keyway fits.