ISO Standard Keyway Dimensions
Reference table of key sizes, shaft diameters, and tolerances for ISO standard keyways in mechanical engineering
ISO Keyway Dimensions Table
| Shaft Diameter (mm) | Key Width b (mm) | Key Height h (mm) | Keyway Depth t1 (mm) | Keyway Depth t2 (mm) |
|---|---|---|---|---|
| 6 – 8 | 2 | 2 | 1.2 | 0.8 |
| 8 – 10 | 3 | 3 | 1.8 | 1.2 |
| 10 – 12 | 4 | 4 | 2.5 | 1.6 |
| 12 – 17 | 5 | 5 | 3.0 | 2.0 |
| 17 – 22 | 6 | 6 | 3.5 | 2.3 |
| 22 – 30 | 8 | 7 | 4.0 | 2.8 |
| 30 – 38 | 10 | 8 | 5.0 | 3.3 |
| 38 – 44 | 12 | 8 | 5.0 | 3.3 |
About ISO Standard Keyways in Mechanical Design
Standardized keyways are critical components in mechanical power transmission systems—used to reliably connect rotating shafts with gears, pulleys, hubs, and couplings. This reference table provides the essential dimensions for rectangular parallel keys and corresponding keyways in accordance with international standards such as ISO R 773 (Rectangular or Square Parallel Keys and their Corresponding Keyways) and related national standards.
Using keyways with precise width, height, and depth specifications ensures proper torque transfer, shaft-hub alignment, and manufacturing compatibility. Accurate keyway sizing helps avoid vibration, wear, failure of components and ensures interchangeability of shaft-mounted parts.
Keyway Dimension Definitions
- Shaft Diameter – The nominal diameter range of the shaft for which the keyway dimensions apply.
- Key Width (b) – The standard width of the rectangular key, influencing torque capacity and fit.
- Key Height (h) – The overall height of the key, affecting engagement depth in both shaft and hub.
- Keyway Depth (t₁) – The depth of the key slot in the shaft, required for correct key insertion and load distribution.
- Keyway Depth (t₂) – The depth of the mating slot in the hub or gear, ensuring key alignment and uniform load transfer.
Engineering & Manufacturing Applications
Designers, mechanical engineers, and machinists use this keyway dimension reference to:
- Select the correct key and keyway sizing based on shaft diameter to ensure proper torque transmission and structural safety.
- Specify tolerances and manufacturing allowances in drawings, CNC programs, and fabrication workflows.
- Ensure compatibility and interchangeability of shafts, gears, pulleys, and couplings across global standards.
- Minimize machining errors, reduce rework, and maintain precise shaft-hub alignment to enhance component longevity.
Whether working in automotive, industrial machinery, robotics, or custom mechanical design, using the correct keyway dimensions and adhering to standard references such as ISO R 773 ensures reliable results, easier sourcing of standard parts, and seamless integration across systems. This chart serves as a quick engineering reference for keyway dimensioning in mechanical design and production.