Parallel Key & Keyway
Look up the parallel-key size and keyway depth by shaft diameter for a torque-transmitting key joint. Find the shaft-diameter range in the first column, then read b×h, t1 (shaft keyway) and t2 (hub keyway).
b×h = key width × height. t1 = keyway depth in the SHAFT, t2 = keyway depth in the HUB (bore).
Parallel key — by shaft diameter (JIS B1301)| Shaft d (mm) | Key b×h (mm) | Shaft t1 (mm) | Hub t2 (mm) |
|---|
| 6–8 | 2×2 | 1.2 | 1.0 |
| 8–10 | 3×3 | 1.8 | 1.4 |
| 10–12 | 4×4 | 2.5 | 1.8 |
| 12–17 | 5×5 | 3.0 | 2.3 |
| 17–22 | 6×6 | 3.5 | 2.8 |
| 22–30 | 8×7 | 4.0 | 3.3 |
| 30–38 | 10×8 | 5.0 | 3.3 |
| 38–44 | 12×8 | 5.0 | 3.3 |
| 44–50 | 14×9 | 5.5 | 3.8 |
| 50–58 | 16×10 | 6.0 | 4.3 |
| 58–65 | 18×11 | 7.0 | 4.4 |
| 65–75 | 20×12 | 7.5 | 4.9 |
| 75–85 | 22×14 | 9.0 | 5.4 |
| 85–95 | 25×14 | 9.0 | 5.4 |
| 95–110 | 28×16 | 10.0 | 6.4 |
Parallel keys per JIS B1301 (≈ ISO 773). Values correspond to the shaft-diameter range in the first column. Key fit (free / normal / close) and keyway tolerances are chosen per requirement — verify against the standard when detailing the drawing.
Frequently asked questions
What key size fits a Ø30 shaft?
Read the row for the diameter range that includes Ø30 to get b×h and the keyway depths t1/t2 per JIS B1301.
What are t1 and t2?
t1 is the keyway depth in the SHAFT, t2 is the depth in the HUB (bore). b×h is the key width × height.
How do I check key strength?
Use the “Parallel key calculator” under Calculators: enter shaft diameter, torque and key size to check shear and bearing stress.
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