KEVOS® MAKEOS · Materials
Differential Thermal Fit
How does clearance change at different part temperatures?
Calculate signed diametral clearance after hole and shaft undergo separate uniform temperature changes from one reference.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Hole diameter at reference temperature | mm | Actual or selected limit hole diameter at the reference temperature. |
| Shaft diameter at reference temperature | mm | Actual or selected limit shaft diameter at the same temperature. |
| Hole-material expansion coefficient | µm/(m·K) | Validated mean linear expansion coefficient for the hole material over its range. |
| Shaft-material expansion coefficient | µm/(m·K) | Validated mean coefficient for the shaft material over its range. |
| Common reference temperature | °C | Common temperature at which both entered diameters apply. |
| Hole operating temperature | °C | Uniform temperature of the hole-carrying part. |
| Shaft operating temperature | °C | Uniform operating shaft temperature. |
Method and formulas
- For each part: diameter at temperature = reference diameter × [1 + coefficient × 10⁻⁶ × temperature change].
- Signed diametral clearance = hole − shaft. Positive is gap; negative is geometric interference.
- Example: 50.02 mm hole with coefficient 23 and 50 mm shaft with coefficient 12, referenced at 20°C and operating at 80°C and 60°C, gives 50.0890276 and 50.024 mm. Clearance = 0.0650276 mm.
Limitations
- Uniform, unrestrained isotropic expansion with constant mean coefficients; gradients, coatings and constraint are excluded.
- Interference is geometric, not a contact-pressure or assembly-force result.
- Coefficients are user-supplied, and the examples do not select materials. Tolerance/temperature corner cases require separate evaluation.
- Default values are worked examples, not recommended settings or material properties.
Typical uses
- operating clearance
- differential expansion
- thermal interference
Who it is for
- Design engineers
- Maintenance engineers
What you get
- Operating diameters
- Reference and operating signed clearance
- Thermal clearance change
Interpreting the result
- Check minimum and maximum clearance across credible size and temperature conditions.
- Verify material data over the complete temperature range.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 375–379. Topic reference; implementation and examples are original, and no source tables are reproduced.
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