How hot do I need to heat a part for a shrink fit?

The bore must grow by at least the diametral interference, so the temperature rise is ΔT = interference/(α·D). For 0.003 in on a 2 in steel part with α = 6.5×10⁻⁶/°F that is 231 °F. Add a margin — typically 50% — so the parts go together without binding.

Can I assemble a shrink fit with liquid nitrogen?

Yes, for parts that cannot be heated. Nitrogen boils at −320 °F, which gives a large contraction. The practical problems are frost and condensation contamination, loss of control over the temperature, and the brittleness that low temperature induces in some materials.

How much interference should I specify?

It depends on the torque to be transmitted and the materials. As a starting point for a steel hub on a steel shaft, 0.001 in per inch of diameter is a light press fit and 0.002 in per inch is a heavy one. The correct value comes from a stress calculation that confirms neither part yields.

What happens if the interference is too great?

The hoop stress in the hub can exceed yield, so the hub expands permanently and the fit is lost — often with a visible crack. The shaft is also in compression and can yield for a thick-walled hub. Both failure modes are checked by comparing the contact pressure against the yield strength of each part.

What temperature limit applies to heating?

Whatever preserves the part's heat treatment and any components already fitted. Tempered steel should generally not exceed about 400 °F, and you must stay well below the tempering temperature of the alloy. Bearings, seals and bonded assemblies have much lower limits and are usually installed after the shrink fit.

Shrink Fit Calculator

Assembly temperature and thermal growth for an interference fit, plus the force needed for a press fit.

Page last changed 2026-10-19 · based on n/a — standard engineering relationships, no single governing revision

Quick Answer

To assemble by heating, the bore must grow by at least the interference: ΔT = interference ÷ (α × D). For 0.003 in of interference on a 2 in steel bore at α = 6.5 × 10⁻⁶/°F, that is a 231 °F temperature rise.

Shrink Fit and Press Fit

Nominal diameter (in)

Diametral interference (in)

Coefficient of thermal expansion (/°F)

Fit length (in)

Friction coefficient

Modulus (psi)

The Formulas Used

Temperature rise: ΔT = interference ÷ (α · D)
Contact pressure (approximate, equal materials, thick-walled): p ≈ E · (δ/D) ÷ 2
Holding force: F ≈ μ · p · π · D · L

Heating, Cooling, or Pressing

Three ways to assemble an interference fit, and the choice is mostly about size and access.

Heating the outer part is the usual method for a hub on a shaft. It needs the least force and produces no galling, but the temperature must stay below anything that changes the material — roughly 300 °F for a tempered steel hub, and much lower for anything with a bearing, seal or coating already fitted.

Cooling the inner part with dry ice or liquid nitrogen works when the outer part cannot be heated, but it is harder to control and frost contamination is a real problem. It also cannot be used on materials that become brittle when cold.

Pressing needs no temperature at all but requires the most force, and the friction of assembly can gall the surfaces and remove material — which reduces the interference you thought you had. Pressing is best reserved for light interference fits and short engagement lengths.

Frequently Asked Questions

How hot do I need to heat a part for a shrink fit?: The bore must grow by at least the diametral interference, so the temperature rise is ΔT = interference/(α·D). For 0.003 in on a 2 in steel part with α = 6.5×10⁻⁶/°F that is 231 °F. Add a margin — typically 50% — so the parts go together without binding.
Can I assemble a shrink fit with liquid nitrogen?: Yes, for parts that cannot be heated. Nitrogen boils at −320 °F, which gives a large contraction. The practical problems are frost and condensation contamination, loss of control over the temperature, and the brittleness that low temperature induces in some materials.
How much interference should I specify?: It depends on the torque to be transmitted and the materials. As a starting point for a steel hub on a steel shaft, 0.001 in per inch of diameter is a light press fit and 0.002 in per inch is a heavy one. The correct value comes from a stress calculation that confirms neither part yields.
What happens if the interference is too great?: The hoop stress in the hub can exceed yield, so the hub expands permanently and the fit is lost — often with a visible crack. The shaft is also in compression and can yield for a thick-walled hub. Both failure modes are checked by comparing the contact pressure against the yield strength of each part.
What temperature limit applies to heating?: Whatever preserves the part's heat treatment and any components already fitted. Tempered steel should generally not exceed about 400 °F, and you must stay well below the tempering temperature of the alloy. Bearings, seals and bonded assemblies have much lower limits and are usually installed after the shrink fit.

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#	Source	Type	Revision / method
[1]	Values computed in your browser	derived	Evaluated locally from the formulas shown on the page. No data leaves the device.

Data Sources

Standard	Revision	What it covers on this page
Formulas as shown on this page	n/a — standard engineering relationships, no single governing revision	every value this calculator produces

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Value	How it is derived
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Plain text

Engineering Reference. "Shrink Fit Calculator." https://refmanual.com/calculators/shrink-fit/ (accessed 2026-10-19). Data from Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision.

BibTeX

@misc{shrink-fit,
  title        = {Shrink Fit Calculator},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/calculators/shrink-fit/}},
  note         = {Accessed: 2026-10-19},
  source       = {Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Shrink Fit Calculator
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/calculators/shrink-fit/
PY  - 2026
DA  - 2026-10-19
N1  - Source: Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision
ER  -