DIN 6885 key sizes, keyway depths and fits for shafts from 6 to 500 mm.
A parallel key locks a hub to a shaft. Its size comes from the shaft diameter, and its length comes from the torque. Find your shaft in the first column to get the key width and height and the depth of the groove in the shaft and the hub. Then check the key for your torque, as the size alone does not tell you what it can carry.
b = key width, h = key height, t1 = keyway depth in shaft, t2 = keyway depth in hub. All dimensions in mm. Each range runs from above the first figure up to and including the second: 30 mm takes 8 × 7. ISO 773 is withdrawn.
| Shaft ⌀ range (mm) | Key b × h (mm) | t1 shaft (mm) | t2 hub (mm) | Key length range (mm) |
|---|---|---|---|---|
| 6–8 | 2 × 2 | 1.2 | 1.0 | 6–20 |
| 8–10 | 3 × 3 | 1.8 | 1.4 | 6–36 |
| 10–12 | 4 × 4 | 2.5 | 1.8 | 8–45 |
| 12–17 | 5 × 5 | 3.0 | 2.3 | 10–56 |
| 17–22 | 6 × 6 | 3.5 | 2.8 | 14–70 |
| 22–30 | 8 × 7 | 4.0 | 3.3 | 18–90 |
| 30–38 | 10 × 8 | 5.0 | 3.3 | 22–110 |
| 38–44 | 12 × 8 | 5.0 | 3.3 | 28–140 |
| 44–50 | 14 × 9 | 5.5 | 3.8 | 36–160 |
| 50–58 | 16 × 10 | 6.0 | 4.3 | 45–180 |
| 58–65 | 18 × 11 | 7.0 | 4.4 | 50–200 |
| 65–75 | 20 × 12 | 7.5 | 4.9 | 56–220 |
| 75–85 | 22 × 14 | 9.0 | 5.4 | 63–250 |
| 85–95 | 25 × 14 | 9.0 | 5.4 | 70–280 |
| 95–110 | 28 × 16 | 10.0 | 6.4 | 80–320 |
| 110–130 | 32 × 18 | 11.0 | 7.4 | 90–360 |
| 130–150 | 36 × 20 | 12.0 | 8.4 | 100–400 |
| 150–170 | 40 × 22 | 13.0 | 9.4 | 100–400 |
| 170–200 | 45 × 25 | 15.0 | 10.4 | 110–450 |
| 200–230 | 50 × 28 | 17.0 | 11.4 | 125–500 |
| 230–260 | 56 × 32 | 20.0 | 12.4 | 140–500 |
| 260–290 | 63 × 32 | 20.0 | 12.4 | 160–500 |
| 290–330 | 70 × 36 | 22.0 | 14.4 | 180–500 |
| 330–380 | 80 × 40 | 25.0 | 15.4 | 200–500 |
| 380–440 | 90 × 45 | 28.0 | 17.4 | 220–500 |
| 440–500 | 100 × 50 | 31.0 | 19.5 | 250–500 |
26 rows
| Fit | Key width | Shaft keyway | Hub keyway | Use |
|---|---|---|---|---|
| Sliding | h9 | H9 | D10 | Hub slides along the shaft |
| Normal | h9 | N9 | JS9 | General use |
| Tight | h9 | P9 | P9 | Reversing or shock loads |
3 rows
You can inspect a keyway with a micrometer or a caliper. Measure across the shaft and the hub:
For a 40 mm shaft, the key is 12 × 8, with t₁ = 5.0 and t₂ = 3.3. So the shaft measures 35.0 mm and the hub measures 43.3 mm. Since 5.0 + 3.3 = 8.3 mm and the key is 8 mm high, the top of the key clears the hub by 0.3 mm. A key that touches the bottom of the hub groove is the wrong key or the wrong groove.
The key can fail by shearing across its width or by crushing the side of a groove. Check both. The force at the shaft surface is F = 2T ÷ d.
Take 300 N·m on a 40 mm shaft, with a 12 × 8 key working over 50 mm:
Crushing is four times the shear stress here, so the hub sets the limit and a check of shear alone would miss it. The depth used is the part of the key inside that groove, so 8 − 5 = 3 mm for the hub.
The keyway dimension calculator runs these checks with your steel and also covers inch keys. Rounded ends do not carry load, so a Form A key works over its length minus its width.
Form A has two round ends, Form B has two square ends, and Form C has one of each. All have the same cross-section. If one key is not enough, a longer key is the first step. Two keys at 180° carry more, but the two do not share the load equally because of machining differences.
A keyway also weakens the shaft, which the shaft diameter calculator lets you allow for. For the groove tolerances in microns, use the ISO fits and tolerances chart.
By O.E. — Partner, chairman of the board and CEO of a metal products manufacturer for 21 years; the company exports to 45 countries.
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Last reviewed
Classification: Standard key and keyway dimensions
Sources
DIN 6885-1, Drive type fastenings without taper action; parallel keys, keyways, deep pattern, as printed in TU Dortmund's extract
DIN
DIN 6885 Keyways, technical sheet
ELESA-GANTER
ISO/R 773:1969 — Rectangular or square parallel keys (withdrawn)
ISO
Key sizes and keyway depths follow DIN 6885-1 for shafts from 6 to 500 mm. Each range runs from above the first figure up to and including the second.
The standard assigns a key cross-section and keyway depths to each shaft range. Key length comes from a shear and bearing check for the torque, not from the table.
Classification: Stable (mature standard)
These values change rarely. Confirm the current edition of the standard for procurement and design.
All key, keyway and shaft dimensions in millimetres.
Go deeper with FlowUtil guides that explain the concepts behind this reference table.
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