Jared MaffucciSenior Mechanical Engineer | Hardware Product Development

Engineering lab · Interactive tool

Thermal Fit + Clearance Calculator.

Track how independent temperatures and material expansion rates shift the diametral relationship between a shaft and bore.

Thermal fit screening / independent component temperatures

Live calculation

01Diameters + materials

02Temperature states

Thermal fit between a shaft and boreConcentric shaft and bore diameters change independently with temperature.SHAFTBOREDIAMETRAL FIT
Uniform linear expansionΔD = D · α · ΔT

Thermal fit results updated. Final clearance 0.04204 millimeters. Final condition Clearance.

Initial clearance0.02 mmbore minus shaft
Final clearance0.04204 mmClearance
Clearance change0.02204 mmthermal shift
Final conditionClearanceBore 25.066 · Shaft 25.024 mm
Revision1.2
AuthorJared Maffucci
Last technical review23 July 2026
Input guardrailsFinite values; nonnegative magnitudes; physical geometry and material domains enforced
UsePreliminary engineering judgment only
Variable definitions
  • D: reference diameter
  • α: thermal expansion coefficient
  • ΔT: temperature change
  • c: diametral clearance
Hand-verified examples
  • Differential expansion: 0.031024 mm final clearance
  • No temperature change: initial clearance remains unchanged
Change log · revision 1.2

Added visible variables, two verification examples, and an experience connection. Calculation method is unchanged.

Related engineering capability

Temperature can reverse a nominal fit

This first-order model applies uniform linear expansion to the bore and shaft independently, making it useful for quick assembly, operating-temperature, or material-pair screening.

For critical fits, apply the full manufacturing tolerance limits and evaluate contact pressure, gradients, transient states, coatings, and constrained deformation.

Before releasing a thermal fit

  • Evaluate hot, cold, startup, shutdown, and assembly states
  • Use temperature-dependent material properties where needed
  • Include full shaft and bore tolerance limits
  • Check interference pressure and material yield
  • Account for gradients, constraint, coatings, wear, and surface finish

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Review the product, the available evidence, and the decision blocking progress.

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