# Shrink Fit Heating Temperature Calculator

> Source: https://netray.co/tools/shrink-fit-heating-temperature-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Calculate how hot a bore must be to slip over a shaft: required expansion, temperature rise and final oven temperature, with the material limits that matter.

## Category

engineering-plm

## Industry

Discrete Manufacturing

## Audience

- Manufacturing engineer
- Assembly technician
- Maintenance engineer

## Tool

**Kind:** calculator

**Inputs:**

#### Bore diameter at room temperature

**Key:** dia

**Type:** number

**Default:** 50

**Min:** 1

**Step:** 1

**Unit:** mm

#### Maximum diametral interference

**Key:** interf

**Type:** number

**Default:** 0.05

**Min:** 0

**Step:** 0.005

**Unit:** mm

**Help:** Largest shaft minus smallest hole, from the fit limits.

#### Assembly clearance wanted when hot

**Key:** clear

**Type:** number

**Default:** 0.03

**Min:** 0

**Step:** 0.005

**Unit:** mm

**Help:** Typical 0.02 to 0.05 mm for small parts, more for large or slow assemblies.

#### Material

**Key:** alpha

**Type:** select

**Default:** 11.7

**Options:**

##### Carbon steel (11.7 per million per C)

**Value:** 11.7

##### Cast iron (10.5)

**Value:** 10.5

##### Stainless 304 (17.3)

**Value:** 17.3

##### Aluminum (23.1)

**Value:** 23.1

##### Bronze (18.0)

**Value:** 18

#### Room temperature

**Key:** room

**Type:** number

**Default:** 20

**Step:** 1

**Unit:** C

#### Allowance for cooling during handling

**Key:** loss

**Type:** slider

**Default:** 15

**Min:** 0

**Max:** 60

**Step:** 5

**Unit:** %

**Help:** Extra rise to cover heat lost before the part is in place.

**Outputs:**

#### Diametral growth needed

**Key:** expansion

**Expr:** interf + clear

**Format:** decimal

**Description:** In mm.

#### Temperature rise needed

**Key:** dt

**Expr:** expansion / (alpha * 0.000001 * dia)

**Format:** number

#### Temperature rise with handling allowance

**Key:** dt_adj

**Expr:** dt * (1 + loss / 100)

**Format:** number

#### Oven setpoint

**Key:** t_final

**Expr:** room + dt_adj

**Format:** number

**Primary:** true

**Description:** In degrees C.

#### Minimum temperature with no heat loss

**Key:** t_nohandle

**Expr:** room + dt

**Format:** number

**Primary:** true

**Chart:**

#### Oven setpoint vs interference (C)

**Type:** line

**X:** interf

**From:** 0.01

**To:** 0.15

**Steps:** 15

**Series:**

- t_final

**Disclaimer:** Uses linear expansion with a constant coefficient. Check the maximum permitted temperature for hardened steel (tempering loss), bearing grease and seals, and coatings. Large parts, alloys and hollow sections may need verification by test.

## Content

**Intro:** In a shrink fit the outer part is heated so the bore grows large enough to slide over the shaft, then it cools and grips. This calculator turns your interference and clearance into an oven temperature.

**Sections:**

#### How to use it

**Body:** Enter the bore diameter, the largest interference the fit can have, and a small clearance so the part can be placed. Choose the material and the room temperature. The tool gives the diametral growth, the temperature rise and an oven setpoint with an allowance for cooling while you move the part. The chart shows how the setpoint climbs with interference, which helps you judge when heating alone is no longer practical and shaft cooling should be added.

#### The formula

**Body:** Linear thermal expansion gives the change in diameter as the coefficient times the diameter times the temperature change. Rearranging, the temperature rise equals the needed growth divided by the product of the coefficient and the diameter. For a 50 mm steel bore with 0.05 mm interference and 0.03 mm clearance, growth is 0.08 mm and the rise is about 137 C, so the final temperature is about 157 C before the handling allowance.

**Bullets:**

- Use the maximum interference to be safe on every part
- Rises above about 250 C can temper hardened steel parts
- Bearings are usually limited to around 120 C
- Cooling the shaft with dry ice or liquid nitrogen adds growth difference

#### Common mistakes

**Body:** People often use the nominal interference instead of the worst case, which leaves the largest shaft stuck halfway. Others heat a thick hub without allowing for the time it takes the core to reach temperature, so the bore is warm but the part is not. Assembly should be quick and aligned, ideally with a stop or fixture. Different materials in the pair matter: if the shaft is aluminum and the hub is steel, the holding force changes with operating temperature. Never exceed the temperature limit of seals or lubricants, and use proper lifting and PPE for hot parts.

**Cta:** If assembly instructions like these live in ERP routings or work instructions, Netray can help turn calculated parameters into controlled operation notes.

**Faq:**

#### How do I calculate shrink fit temperature?

**Answer:** Divide the diametral growth you need (interference plus clearance) by the product of the thermal expansion coefficient and the bore diameter. Add the result to room temperature. For a 50 mm steel bore needing 0.08 mm, the rise is roughly 137 C.

#### What is the maximum safe temperature to heat steel for a shrink fit?

**Answer:** Many shops stay below about 250 to 300 C to avoid tempering and surface oxidation of hardened parts. Always check the heat treatment and any coating on the specific component, and do not exceed the limit of seals, bearings or grease.

#### When should I cool the shaft instead?

**Answer:** When the heating needed is too high or the hub cannot be heated safely. Cooling the shaft with dry ice or liquid nitrogen shrinks it and can be combined with moderate heating of the hub. Use the same formula with the shaft coefficient and a negative temperature change.

#### Does this give the holding torque?

**Answer:** No. Holding capacity depends on contact pressure, friction coefficient, length and material stiffness. This tool only calculates the heating needed to assemble the parts.

## Search terms

shrink fit calculator, shrink fit heating temperature, interference fit heating calculator, how hot to heat a gear for shrink fit, thermal expansion shrink fit, bearing heating temperature, shrink fit assembly clearance, cooling shaft liquid nitrogen shrink fit

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