What is the difference between a keyway and a keyseat?

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

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

Use the standard and edition required by the controlled drawing. ASME B17.1-1967 (S2023) is the current reaffirmed inch reference listed by ANSI. DIN Media lists DIN 6885-1:2021-11 as the current metric deep-pattern edition. The metric table in this free lookup is explicitly a legacy 1968 geometry reference, not a reproduction of the licensed 2021 edition.

What key fit tolerances are shown?

The result provides reference fit designations only. Numeric deviations depend on the selected fit, nominal size and applicable standard edition; obtain them from the controlled drawing or current licensed standard before machining.

My shaft diameter is exactly on a range boundary — which row applies?

Each displayed interval is lower-exclusive and upper-inclusive: min < d ≤ max. For example, 8.000 mm moves to the row ending at 8 mm, while any value greater than 8 mm moves to the next row.

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?

No. Treat the output as a preliminary lookup. Confirm the current standard edition, selected fit, numeric deviations, corner radii, key length, material and drawing requirements before creating a CNC program or releasing a part.

Keyway Size Calculator

Enter a shaft diameter to find a preliminary nominal parallel-key size and shaft-keyseat depth. The inch lookup is aligned to the ASME B17.1 size relationship; the metric lookup reproduces legacy DIN 6885-1:1968 geometry and must be checked against DIN 6885-1:2021-11 before manufacturing.

Shaft Input

Standard

Shaft Diameter (inches)

Quick examples

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

Copied!

Summary

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 selects the table interval that actually contains the entered diameter; it does not round to a nearby shaft size.
Nominal key width/height and the shaft-keyseat depth are displayed with edition and fit guidance.
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: 2026-09-19 · Reviewed by Nham Vu

Keyway Size Calculator

Shaft Input

Dimensions

Fit guidance — verify numeric limits

Summary

How it works

Use cases

Frequently Asked Questions

Keyway Size Calculator

Use the Keyway Size Calculator

Shaft Input

Dimensions

Fit guidance — verify numeric limits

Summary

How it works

Use cases

Frequently Asked Questions