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Calculations

Estimate free thermal expansion of a bore

Estimate the bore temperature that would remove an assumed diametral interference and add a specified clearance. This is a linear expansion model, not a safe mounting temperature or joint-strength calculation.

Enter values →Sources and scope ↓

Your inputs

Your result

Enter known values and calculate. Source examples are available above.

Formula and worked example

Assume D = 50 mm, interference = 0.02 mm, installation clearance = 0.01 mm, α = 12 µm/m/K and initial temperature = 20 °C. Growth = 0.03 mm, rise = 50 K and estimated bore temperature = 70 °C. These are assumed inputs, not a material or mounting recommendation.

Model assumptions

The bore heats freely and uniformly, its expansion coefficient is approximately constant over the interval, and the shaft stays at the initial temperature. The model ignores transfer cooling, gradients, restraints and contact stress.

Choose inputs for the actual material

Supply the coefficient for the actual material and temperature interval; no “steel” value is selected for you. Check the part-maker’s heating limits, seals, lubrication, heat treatment and mounting method separately.

Equation

Required diameter growth = interference + installation clearance. Temperature rise ΔT = growth / (initial bore diameter × α × 10⁻⁶), with α in µm/m/K. Estimated temperature = initial temperature + ΔT.

Continue your task

Calculate clearance from hole and shaft limits →Interference fit: distinguish size overlap from capacity →

All tolerance and surface references →

Sources and review scope

Reviewed 23 October 2026. Arithmetic examples are labelled separately from source-table facts and standard scope.

NIST — Uncertainty and Dimensional Calibrations

Printed p. 650, equation (1): linear temperature correction and coefficient/temperature uncertainty. Heating model here is an algebraic estimate, not a mounting procedure.

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