Keyway Depth Calculator for Shafts and Hubs

🔧 Keyway Depth Calculator

Match DIN 6885-A shaft key sizes to a clean shaft depth, hub depth, cutter depth, and pass count before you machine the slot.

📌 Presets

Common workshop shaft sizes and key widths, ready to load with one click.

📊 Calculator

The lookup follows the DIN 6885-A keyway table and converts everything into the unit you choose for setup.

Machining Method

Select the machine style that best matches the cut.

Fit Class

Side clearance note for the key-to-slot feel.

Shaft diameter

Used to select the standard DIN 6885-A row.

Key length

Use this to check the engagement ratio.

Cutter diameter

Should not exceed the key width after fit allowance.

Max pass depth

Controls the roughing and cleanup pass count.

Finish allowance

Leave a little material for a final cleanup pass.

Key width tolerance

Matches the fit class note for the slot width.

Optional clearance

Optional side allowance for a looser assembly.

Table note

Use the standard name for quick reference.

Keyway Results

Standard Key Size

DIN 6885-A match

Shaft Keyway Depth

Depth from the shaft OD

Hub Keyway Depth

Nominal complementary depth

Pass Count

Based on your max pass depth

🛠 Tooling Grid

Pick the machine method that best matches your setup. The result is a nominal depth target, not a tolerance callout.

Broach

Best for

Production pulls and repeatable slots

End Mill

Best for

Flexible one-off jobs and cleanup passes

Keyseat Cutter

Best for

Classic shaft keyseats and narrow slots

Slotter

Best for

Slow, deliberate manual milling work

📐 DIN 6885-A Reference Table

The table below mirrors the standard metric ranges used in the calculator. The live result converts the same data into imperial when needed.

Shaft Diameter	Key Size	Shaft Depth	Hub Depth	Typical Use

📊 Fit Reference

Fit class does not change the nominal table depth, but it helps you judge the side clearance before you commit to the cut.

Fit Class	Allowance	Typical Feel	Best Use
Loose	+0.05 mm / +0.002 in	Easy assembly	Field repairs and quick checks
Standard	+0.02 mm / +0.001 in	Balanced fit	General workshop keyways
Tight	0.00 mm / 0.000 in	Firm seating	Precision shafts and hubs
Hand Fit	0.00 mm / 0.000 in	Scrape or stone	Final fitting after test assembly

📝 Formula Reference

These are the calculations used in the live result. They keep the worksheet readable when you need to sanity-check the numbers by hand.

Formula	Meaning	What It Returns	Use
Lookup row	Match shaft dia to table	Key width and height	Standard selection
Hub depth	Key height - shaft depth	Nominal hub seat depth	Complementary fit
Cut depth	Nominal depth + allowance	Finish-ready depth	Cleanup pass target
Pass count	Cut depth / max pass	Rounded up whole passes	Machining plan
Engagement ratio	Key length / key width	Length to width ratio	Check key support

💡 Tips

Tip: Round up to the next standard row instead of forcing a custom depth in the middle of a catalog size.

Tip: If the cutter is wider than the key width, stop and pick the correct tool before you cut metal.

Tip: Leave a little finish allowance when you need a smoother fit or a final hand scrape.

Tip: Use the pass count to keep the cut shallow enough for stable chip control.

The calculator returns nominal keyway depths for setup and layout. Always confirm the drawing tolerance, inspect the actual key stock, and verify fit before final assembly.

⚠ Safety Note

Always secure the workpiece, keep hands clear of the cutter path, and confirm the shaft and hub dimensions before machining. Never rely on the calculator alone when a print specifies a tighter tolerance.

📖 Article

This keyway depth calculator matches DIN 6885-A shaft sizes to nominal shaft and hub depths, then converts the setup into a pass count, fit note, and cutter check for faster workshop planning.

The depth of keyway is one of those important details when you work with shafts, hubs and keys in machining. Right choices ensure that parts fit well and transmit torque without problems.

Depth of keyway is strictly standardized. For shafts according to the usual basic system, the width tolerance of shaft keyway is h9. Metric keys and keyway sizes follow ISO/R773 with Js9 for width. A keyway calculator app finds exactly the depth of keyseat for shaft and hub together with tolerances according to ANSI/ASME B17.1-1967 standard.

Measuring and Cutting Keyway Depth

For total keyway depth you calculate the arch height of shaft, called dimension A. Because you can directly measure from keyway bottom to opposite spot on shaft, it gives the most precise value. Square keyway divided by four, times shaft size, gives chord depth inside.001 inches

Dimension S shows shaft keyseat bottom to opposite shaft side. Dimension T measures hub keyway bottom to opposite hub bore side. Because keyseats taper, T is taken at the deepest end.

Half of key thickness plus.005 inches for depth is usual practice, if nothing otherwise marked on design. Most of shaft keyways have depth half of key height plus.010 inches. For half-inch key depth is.250 plus.010, so.260 inches.

Keyway for three-quarter-inch shafts have 3/16 inch width, 3/32 inch depth with 3/16 inch square key.

The table shows nominal shaft diameters of 6 mm until 500 mm together with recommended key sizes, keyway widths, heights, depths and tolerances. Surface finish in keyway sides and bottom does not surpass 250 microinches.

Cutting keyway, the endmill must match around with keyway size. First touch shaft top by means of endmill, go down until perfect circle up, later half of endmill diameter in depth. Do light slices until wanted depth.

Keyway broaches by means of tool holder on lathe, moving carriage inside and outside. With Bridgeport and right cutter, work lasts around 15 minutes. Depth dimension usually does not mark directly on designs, but calculates from center line of bore to keyway top from whole bore size

Author

Thomas Martinez

Hi, I am Thomas Martinez, the owner of ToolCroze.com! As a passionate DIY enthusiast and a firm believer in the power of quality tools, I created this platform to share my knowledge and experiences with fellow craftsmen and handywomen alike.

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