Shrink fit temperature calculator
Heating the outer part or chilling the inner one buys a few tenths of a millimetre — enough to assemble an interference fit without force.
per K
Temperature change needed
166.7K
- Heat the outer part to
- 187 degrees C
- Or chill the inner part to
- -147 degrees C
- Approximate contact pressure
- 100.0 MPa
- Axial holding force
- 141 372
- Holding torque
- 3534.3 N m
- Contact area
- 9425 mm2
Show the working
- Nominal diameter = 50
- Diametral interference = 0.05
- Assembly clearance wanted = 0.05
- Expansion coefficient = 0.000 012
- Engagement length = 60
- Coefficient of friction = 0.15
- Temperature change needed = (0.05 + 0.05) / (50 * 0.000 012) = 166.667
- Heat the outer part to = 20 + 166.667 = 186.667
- Or chill the inner part to = 20 - 166.667 = -146.667
- strain = 0.05 / 50 = 0.001
- Approximate contact pressure = 0.001 * 200000 / 2 = 100
- Contact area = pi * 50 * 60 = 9424.78
- Axial holding force = 100 * 9424.78 * 0.15 = 141 372
- Holding torque = 141 372 * 50 / 2000 = 3534.29
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- delta T = (interference + clearance) / (diameter x expansion coefficient)
- contact pressure is roughly E x interference / (2 x diameter) for a thick-walled hub
Above about 250 degrees Celsius many steels start to lose temper. Liquid nitrogen chilling to -196 degrees is the alternative for large interferences.
The pressure figure is a first approximation; a full Lame thick-cylinder analysis accounts for the hub wall thickness.