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.

Data verified 2026-09-29 · 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.

Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

#	Source	Type	Revision / method
[1]	ASME B1.1 — Unified Inch Screw Threads	standard	ASME B1.1-2019 — source
[2]	ASTM A615 — Deformed steel bars for concrete reinforcement	standard	ASTM A615/A615M-20 — source
[3]	ASTM E140 — Hardness Conversion Tables	standard	ASTM E140-12b — source
[4]	Values computed in your browser	derived	Evaluated locally from the formulas shown on the page. No data leaves the device.
[5]	ISO 4287 — Surface texture: Profile method	standard	ISO 4287:1997 — source
[6]	ISO 68-1 — Basic profile	standard	ISO 68-1:2023 — source
[7]	NFPA 70 NEC Table 310.16	standard	NEC 2023 (NFPA 70-2023) — source

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

Cross-checked against:

Formulas verified against the corresponding reference chart on this site, so the calculator and the published tables agree

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
All outputs	Computed in the browser from the formulas above. No data leaves the device.

Outputs are computed from the formulas shown. Verify against the governing standard for design or acceptance work.

Accuracy and use. The values on this page are compiled from the published standards and cross-checked sources listed above. Where values are derived, the derivation is stated. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Every value on this page is traceable to the sources listed above. If you use the data in a document, paper or report, cite it as:

Plain text

Engineering Reference. "Shrink Fit Calculator." https://refmanual.com/calculators/shrink-fit/ (accessed 2026-09-29). 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: 2026-09-29},
  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  - 2026-09-29
N1  - Source: Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision
ER  -

Each row in the tables above also has a permanent link — hover a row and use the # link to cite a single value rather than the whole page.