Thermal Growth Fit Impact Calculator - Shaft & Housing Expansion
Calculate thermal expansion of shafts and housings and see the effect on bearing fit at operating temperature
Free thermal growth calculator that shows how temperature changes affect shaft and housing dimensions and the resulting impact on bearing fit. Enter the shaft material, housing material, nominal dimensions, ambient temperature, and operating temperature. The calculator computes dimensional growth using the coefficient of thermal expansion (CTE) for each material and shows the hot-running fit compared to the cold assembly fit. This is critical for bearing applications because the fit that is correct at room temperature may be too tight or too loose at operating temperature. Steel shafts in aluminum housings are a classic problem: aluminum expands roughly twice as fast as steel, so a bearing that is properly housed at 20°C can be loose in the housing at 80°C. Conversely, a steel shaft running hot inside a steel housing that stays cool tightens the inner ring fit beyond what was intended. The calculator handles steel, stainless steel, aluminum, cast iron, bronze, and copper housing and shaft materials.
Check shaft-to-bore fit against ISO tolerance classes
Press Fit / Clearance Checker →Estimate press or pull force for bearing installation
Bearing Puller Force Estimator →Calculate expected bearing life at operating conditions
L10 Bearing Life Calculator →How It Works
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Select Materials
Choose the shaft material and housing material. Common combinations include steel shaft in cast iron housing, steel shaft in aluminum housing, and stainless shaft in steel housing. Each material has a different CTE.
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Enter Dimensions
Input the shaft diameter and housing bore diameter at room temperature. These are the cold assembly dimensions.
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Enter Temperatures
Input the ambient (assembly) temperature and the operating temperatures for the shaft and housing. The shaft is usually hotter than the housing because it conducts heat from the process. The housing temperature depends on cooling and ambient conditions.
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Review Thermal Growth
See the dimensional change for both the shaft and housing, the resulting hot-running fit, and how it compares to the cold assembly fit. The calculator shows whether the fit tightens or loosens with temperature.
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Evaluate Fit Impact
The calculator flags potential problems: inner ring fit that tightens enough to eliminate internal clearance, or housing fit that loosens enough to cause outer ring creep. Recommendations for bearing clearance class and fit adjustments are provided.
Built For
- Mechanical engineers designing bearing arrangements for equipment with significant temperature rise
- Maintenance engineers investigating bearing failures in high-temperature applications
- Reliability teams evaluating fit conditions for pumps, motors, fans, and gearboxes
- Millwrights selecting bearing clearance class (C3, C4) based on expected thermal growth
- Application engineers checking aluminum housing designs for bearing fit at operating temperature
Frequently Asked Questions
Learn More
Bearing Fits: Why Thousandths of an Inch Matter
How to get the shaft fit right, why loose or tight fits cause different problems, and how thermal growth changes the fit at operating temperature.
Thermal Growth and Bearings: What Changes When Machines Heat Up
How temperature affects shaft fit, housing fit, alignment, and internal clearance. CTE values for common materials and when to use C3 or C4 clearance bearings.
Bearing Installation: Getting It Right Without Damaging the Bearing
Pressing, heating, pulling, and the installation mistakes that create the next failure. When to use an induction heater versus a hydraulic press.
Bearing Removal Force: How Much Pull Does It Take?
Estimating press and pull force for safe bearing installation and removal. When to use mechanical pullers, hydraulic pullers, or induction heating.
Coupling Alignment: Offset, Angularity & Tolerance by Type
Shaft alignment fundamentals: offset vs angularity, tolerance standards by coupling type, rim-and-face vs reverse indicator vs laser methods, and thermal growth compensation.
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