What is the difference between a keyway and a keyseat?

A keyway is the slot cut into the shaft, and a keyseat is the matching slot cut into the hub, bore, or gear. Together they form the key seat pair. In common usage the terms are often used interchangeably.

Which standard should I use — ANSI B17.1 or DIN 6885?

Use ANSI B17.1 for inch-based designs (common in North America) and DIN 6885 for metric designs (common in Europe and international OEM work). Always match the standard to the shaft and key stock already in use.

What key fit tolerances are shown?

ANSI B17.1 specifies Class 1 (loose), Class 2 (normal), and Class 3 (tight) fits. DIN 6885 uses tolerance zones — typically N9 (normal) and JS9 (sliding) for the hub keyseat width. This tool shows the most commonly used normal fit for each standard.

My shaft diameter falls between two table entries — which row applies?

Always use the row whose upper limit is greater than or equal to your shaft diameter. The tool does this automatically by selecting the first range that contains your input.

Does this cover Woodruff (semi-circular) keys?

No. This tool covers parallel rectangular keys per ANSI B17.1 and DIN 6885. Woodruff key dimensions are defined in a separate standard (ANSI B17.2 / DIN 6888) and require a different calculation.

Can I use these dimensions directly for CNC programming?

Yes, the nominal dimensions and tolerances given are taken directly from the published standards and are suitable for use in technical drawings and CNC setup sheets. Always verify against the current edition of the standard for safety-critical applications.

Keyway Size Calculator

Name: Keyway Size Calculator
Availability: InStock
Author: Nham Vu

Enter a shaft diameter to instantly look up the standard keyway width, keyseat depth, hub depth, and fit tolerances per ANSI B17.1 / DIN 6885.

Shaft Input

Standard

Shaft Diameter (inches)

Quick examples

Enter a shaft diameter on the left to see standard keyway dimensions.

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Summary

Enter a shaft diameter to instantly look up the standard keyway width, keyseat depth, hub depth, and fit tolerances per ANSI B17.1 / DIN 6885.

How it works

Enter the shaft diameter in either inches (ANSI) or millimeters (DIN/metric).
Select the applicable standard: ANSI B17.1 or DIN 6885.
The tool matches your diameter to the nearest standard range in the lookup table.
Keyway width, shaft keyseat depth, hub keyseat depth, and fit tolerances are displayed instantly.
Copy any value to clipboard with one click for use in drawings or CNC programs.

Use cases

Selecting keyway dimensions during mechanical shaft design.
Verifying dimensions on a machinist or engineering drawing.
Specifying key stock size when ordering hardware.
Cross-checking ANSI vs. DIN equivalents on international projects.
Teaching students standard shaft-key fitting principles.
Quick field reference on a tablet or phone without paper charts.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu