How to use this calculator
- Enter the shaft diameter. Enter the nominal shaft diameter.
- Choose the fit class. Pick free, normal or close to get the matching tolerance grades.
- Read the dimensions. Read the key width and height, the shaft and hub keyway depths, and the shaft diameter under the keyway for setting cutter depth.
How it works
A parallel (rectangular) key transmits torque between a shaft and a hub through a
slot — the keyway — cut into both. DIN 6885-1 standardises the key cross-section and
keyway depths by shaft diameter range: pick the range your shaft
falls in and you get the key width b, height h, shaft
keyway depth t₁ and hub keyway depth t₂. The shaft is
machined to a depth-under-keyway of d − t₁, and the hub bore over the
keyway is bore + t₂. Using the standard size keeps stock keys, cutters
and broaches interchangeable.
Keyway size is only the geometry step in the shaft/hub workflow. Check the shaft diameter and transmitted torque with the shaft diameter calculator or shaft torsion calculator, then use the press fit calculator or hole and shaft fit calculator when the hub also depends on an interference or clearance fit.
Keyway chart, key size and depth by shaft diameter
This calculator is the searchable keyway chart form of the DIN 6885 table: enter a shaft diameter and it returns the standard key size, keyway width, shaft keyway depth and hub keyway depth. Queries like keyway size chart, shaft key size calculator, keyway depth calculator and standard keyway dimensions all reduce to the same lookup by shaft diameter range. The exact-entry pages keyway size chart and keyway dimensions by shaft size route those searches into this calculator.
Worked example
Verified against the live calculator
A 40 mm shaft falls in the “over 38 to 44 mm” range, so it takes a
12 × 8 mm key. The shaft keyway depth is t₁ = 5.0 mm
(machine the shaft to 35.0 mm under the keyway) and the hub keyway depth is
t₂ = 3.3 mm (bore plus keyway = 43.3 mm). Cut both with a 12 mm-wide
cutter or broach. The calculator returns this directly.
Reference data
DIN 6885-1 parallel keys by shaft diameter. b = width, h = height, t₁ = shaft keyway depth, t₂ = hub keyway depth.
| Shaft Ø (mm) | Key b × h (mm) | Shaft depth t₁ | Hub depth t₂ |
|---|---|---|---|
| > 6 – 8 | 2 × 2 | 1.2 | 1 |
| > 8 – 10 | 3 × 3 | 1.8 | 1.4 |
| > 10 – 12 | 4 × 4 | 2.5 | 1.8 |
| > 12 – 17 | 5 × 5 | 3 | 2.3 |
| > 17 – 22 | 6 × 6 | 3.5 | 2.8 |
| > 22 – 30 | 8 × 7 | 4 | 3.3 |
| > 30 – 38 | 10 × 8 | 5 | 3.3 |
| > 38 – 44 | 12 × 8 | 5 | 3.3 |
| > 44 – 50 | 14 × 9 | 5.5 | 3.8 |
| > 50 – 58 | 16 × 10 | 6 | 4.3 |
| > 58 – 65 | 18 × 11 | 7 | 4.4 |
| > 65 – 75 | 20 × 12 | 7.5 | 4.9 |
| > 75 – 85 | 22 × 14 | 9 | 5.4 |
| > 85 – 95 | 25 × 14 | 9 | 5.4 |
| > 95 – 110 | 28 × 16 | 10 | 6.4 |
| > 110 – 130 | 32 × 18 | 11 | 7.4 |
Source: DIN 6885-1 parallel-key series. Verify against DIN 6885-1 and the part drawing; the fit/tolerance class is specified separately.
Frequently asked questions
How do I find the right keyway size for a shaft?
Enter the shaft diameter. DIN 6885-1 assigns a standard parallel key by diameter range — for example a 40 mm shaft takes a 12 × 8 mm key with a 5.0 mm shaft keyway.
What are t₁ and t₂?
t₁ is the keyway depth cut into the shaft (from the shaft surface), and t₂ is the keyway depth in the hub (from the bore). Together they accommodate the key height plus running clearance.
How deep do I cut the keyway in the shaft?
Cut to a shaft diameter under the keyway of d − t₁. The calculator shows that "shaft Ø under keyway" value so you can set the cutter depth directly.
What width cutter or broach do I need?
The cutter or broach width equals the key width b — 12 mm for the 40 mm shaft example.
Which fit class should I use?
Normal (shaft N9 / hub JS9) is the usual choice. Use Free (H9/D10) for guided or sliding keys, and Close (P9/P9) for reversing or shock loads. The fit sets the width tolerance, not the nominal size.
Is this DIN or ANSI?
This uses the DIN 6885-1 metric parallel-key series. ANSI inch keys (ASME B17.1) use different sizes; toggle to imperial to read the DIN dimensions in inches.
Method & assumptions
- Parallel (rectangular) keys per DIN 6885-1; Woodruff, tapered and gib-head keys differ.
- The fit class sets width tolerances (free H9/D10, normal N9/JS9, close P9/P9); the nominal key and keyway sizes are the same across fits.
- Torque capacity (shear and bearing on the key) is a separate check — use a long enough key for the load and verify the shaft/hub fit separately.