Shrink Fit Temperature Calculator
Heating temperature for a shrink fit or cooling temperature for an expansion fit from the interference and the thermal expansion coefficients, plus size change by temperature
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Hub heating temperature for a shrink fit, shaft cooling temperature for an expansion fit, or a combination, from the interference and the expansion coefficients, with the diameters by temperature as a table and chart. For shrink-fitting a bearing, gear or bushing.
How to use
- On "Shrink and expansion fit" enter "Nominal diameter d", "Interference δ (on diameter)", "Assembly clearance c" and "Room temperature T0".
- Choose the "Hole (hub) material" and "Shaft material"; the coefficients are filled with representative values you can replace.
- Under "Method" choose "Heat the hub", "Cool the shaft" or "Heat and cool", then read the temperature, the cooling medium check and the "Diameter by temperature" table and chart.
- On "Size change by temperature" enter a length or diameter, material and temperatures to get ΔL.
How it works
- ΔT = (δ + c) ÷ (α × d). The hub starts from the hole size d − δ, the shaft from d; L(T) = L0 × (1 + α × (T − T0)). α is entered in µm/m·K (10⁻⁶/K).
- The listed coefficients are representative near room temperature and differ by about ±10 % with alloy and temperature range. Reachability is compared with dry ice at −78.5 °C and liquid nitrogen at −196 °C.
- Only linear expansion is calculated; uneven temperature, contact pressure and fit stresses are not covered.
Questions and answers
- How is the shrink-fit temperature calculated?
- ΔT = (interference + clearance) ÷ (coefficient × diameter). A 50 mm steel hub with 0.05 mm interference and 0.02 mm clearance needs 0.07 ÷ (11.7 × 10⁻⁶ × 49.95) ≈ 120 K, so about 140 °C from 20 °C.
- How much assembly clearance should I allow?
- About 0.0005 to 0.001 times the diameter, so 0.025 to 0.05 mm at 50 mm.
- Can I assemble by cooling the shaft alone?
- A steel shaft shrinks by about 0.11 % of its diameter in dry ice and 0.25 % in liquid nitrogen. For a larger interference the hub must be heated as well.
- What changes with an aluminium hub on a steel shaft?
- Aluminium expands about twice as much as steel (23 against 11.7 µm/m·K), so the hub needs about half the temperature rise. At higher service temperatures the interference shrinks; check it on the "Size change by temperature" tab.