Interference Shrink-Fit Temperature
Heating temperature (or chilling temperature) to open an interference fit enough to assemble a hub, bearing.
Example
You enter
- Nominal fit diameter (in) 4
- Diametral interference (in) 0.004
- Assembly clearance (in) 0.002
- CTE (per °F) 0.0000065
- Ambient temperature (°F) 70
You get
- Required temperature change 231 degF
- Heat outer part to 301 degF
Checked against published worked examples from: Industrial Monitor Direct.
Details, formula, and sources
ScopeHeating temperature (or chilling temperature) to open an interference fit enough to assemble a hub, bearing, or bushing by hand, from the thermal-growth relation delta_dia = alpha x dia x delta_T (steel alpha 6.5e-6/degF). Sizes only the assembly temperature; a separate Lame contact-pressure check governs the holding capacity.
Formula or tableRequired temperature change delta_T = (interference + assembly clearance) / (alpha x nominal diameter); heat the outer/bore part to ambient + delta_T, or chill the inner/shaft part to ambient - delta_T. From delta_dia = alpha x dia x delta_T.
Source and editionInterference shrink-fit assembly temperature - first-principles thermal-expansion relation delta_dia = alpha x dia x delta_T (steel alpha 6.5e-6 per degF), by name; public domain.
Free accessPure thermal-expansion arithmetic, public; the diameter, interference, clearance, coefficient, and ambient are user-supplied.
What governsEstimate. AHJ and licensed professional govern.
API field namesnominal_dia_in, interference_in, clearance_in, alpha_per_f, ambient_f, delta_t_f, heat_to_f
- Coefficient of thermal expansion default 6.5e-6 per degF (steel); editable for the alloypublished material data
- Ambient default 70 degF; a chill below dry ice (-109 degF) needs liquid nitrogenfirst-principles