KEVOS® MAKEOS · Strength
Shrink or Press Fit Design from Required Torque
What interference does a hub need to transmit this torque and thrust, will the hub survive it, and how hot must it be to assemble?
Design of a cylindrical interference fit working backwards from the duty: the interface pressure needed for the torque and axial load with a safety factor, the diametral interference that produces it (Lamé thick-cylinder theory, solid or hollow shaft), hub bore stresses with a von Mises check, the press-in force, and the hub heating temperature for a shrink fit with assembly clearance.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Duty | ||
| Torque to transmit | N·m | Torque the fit must carry. |
| Axial load to transmit | kN | Axial force the fit must carry. |
| Safety factor on slip | Safety factor against slip. | |
| Geometry and materials | ||
| Interface diameter | mm | Nominal diameter at the interface. |
| Shaft bore (0 = solid) | mm | Bore of a hollow shaft. |
| Hub outside diameter | mm | Outside diameter of the hub. |
| Engaged length | mm | Length of the fit. |
| Friction coefficient at the interface | Coefficient of friction at the interface (about 0.1–0.2 for dry steel press fits; shrink fits often higher). | |
| Hub modulus | GPa | Elastic modulus of the hub. |
| Hub Poisson’s ratio | Poisson’s ratio of the hub. | |
| Shaft modulus | GPa | Elastic modulus of the shaft. |
| Shaft Poisson’s ratio | Poisson’s ratio of the shaft. | |
| Hub yield strength | MPa | Yield strength of the hub material. |
| Assembly | ||
| Hub expansion coefficient | µm/m·K | Linear expansion coefficient of the hub. |
| Assembly clearance wanted (diametral) | mm | Clearance needed to slide the hot hub on. |
| Shaft (ambient) temperature | °C | Starting temperature of the parts. |
Method and formulas
- Pressure for the duty: p = n √[(2T ÷ d)² + F_a²] ÷ (π d L μ).
- Interference δ = p d {[(D² + d²) ÷ (D² − d²) + ν_h] ÷ E_h + [(d² + d_i²) ÷ (d² − d_i²) − ν_s] ÷ E_s}.
- Hub bore hoop stress σ_t = p (D² + d²) ÷ (D² − d²); von Mises with the radial −p: √(σ_t² + σ_t p + p²).
- Press force = π d L μ p; hub temperature rise = (δ + clearance) ÷ (α d).
- Example: 500 N·m on a 50 mm fit 60 mm long needs 18.313 µm of interference.
Limitations
- Uniform pressure over the length; hub ends and keyways raise local stresses.
- Surface smoothing reduces effective interference; add roughness allowance.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Specify the interference for a gear, coupling or sleeve on a shaft
- Check that the hub can take the interference needed
- Set the induction or oven temperature for assembly
Who it is for
- Design engineers
- Mechanical engineers
- Engineering managers
What you get
- Required pressure and interference
- Hub stress check
- Press force and shrink-fit temperature
Interpreting the result
- Specify the minimum interference from this result and check the maximum interference against hub yield.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 631–633, 2442–2444. Topic reference; no source tables or recommended settings are reproduced.
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