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Press Fit / Clearance Checker - Shaft-to-Bore Tolerance Verification

Check interference or clearance between shaft and bore against ISO/ANSI tolerance classes

Free press fit and clearance fit checker for verifying shaft-to-bore dimensional compatibility. Enter the measured shaft diameter and bore diameter to instantly determine whether you have an interference fit (press fit), transition fit, or clearance fit, and how much interference or clearance exists. The calculator compares your actual measurements against ISO/ANSI tolerance classes for common bearing mounting applications: shaft fits j5, k5, m5, m6, n6, p6, and bore fits H6, H7, J7, K7, M7, N7, P7. For bearing installations, proper fit is critical. Too loose and the inner ring creeps on the shaft, wearing both surfaces. Too tight and radial preload reduces internal clearance, increasing temperature and shortening life. This calculator shows the resulting fit condition, interference or clearance range, recommended assembly method (hand push, light press, heavy press, or thermal), and warnings if the fit is outside normal bearing mounting practice.

Pro Tip: Before pressing a bearing onto a shaft, measure both the shaft and the bearing bore with a micrometer, not calipers. The fit tolerance is measured in tenths of a thousandth, and calipers are not accurate enough. A shaft that measures 0.0005" over nominal can mean the difference between a proper j5 fit and an overly tight m6 fit that preloads the bearing.

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Press Fit / Clearance Checker
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How It Works

  1. Enter Shaft Diameter

    Input the measured shaft diameter in millimeters or inches. Use a micrometer for best accuracy. Take measurements at multiple points around the circumference and along the length to check for taper and out-of-round.

  2. Enter Bore Diameter

    Input the measured bearing bore or housing bore diameter. For new bearings, this is the catalog nominal bore. For used bearings or housings, measure the actual bore diameter.

  3. Enter Nominal Size

    Input the nominal dimension for the fit. This is the design size that both the shaft and bore are machined to, before tolerances are applied.

  4. Select Tolerance Class

    Choose from standard ISO/ANSI shaft and bore tolerance classes for bearing mounting. The calculator shows the allowable range for each class and whether your measurements fall within spec.

  5. Review Fit Condition

    Get the fit type (interference, transition, or clearance), the amount of interference or clearance, the recommended assembly method, and warnings if the fit is abnormal for bearing mounting.

Built For

  • Millwrights verifying shaft and bearing fit before installation during equipment repair
  • Machinists checking shaft dimensions against bearing fit requirements after turning or grinding
  • Maintenance engineers investigating bearing creep or spin caused by loose fits
  • Quality inspectors verifying shaft tolerance compliance for incoming parts
  • Design engineers selecting the correct tolerance class for bearing mounting in new equipment

Frequently Asked Questions

For rotating shaft applications with normal loads, k5 or m5 is standard for ball bearings and m6 or n6 for roller bearings. For heavy loads or shock loading, step up to n6 or p6. For light loads or easy assembly requirements, j5 provides a light interference that still prevents creep. The tighter the fit, the more the internal clearance is reduced, so use C3 internal clearance bearings with tight shaft fits.
The inner ring creeps (rotates slowly relative to the shaft), wearing both the shaft and the bore surface. This creates fretting corrosion (red-brown rust-like debris), increases vibration, and can lead to the bearing walking off the shaft. If you find fretting marks on a shaft during disassembly, the fit was too loose.
Excessive interference reduces the bearing internal clearance. At extreme interference, the internal clearance goes to zero or even negative (preload). This increases rolling friction, generates excess heat, reduces lubricant life, and dramatically shortens bearing life. If a bearing runs hotter than expected right after installation, check that the shaft fit did not eliminate the internal clearance.
When the interference exceeds what can be achieved by pressing without risk of damaging the bearing. For interference above about 0.001 inch per inch of shaft diameter, heat the bearing to 100-120°C (210-250°F) using an induction heater. Never use a torch - uneven heating damages the bearing steel. The bearing expands, slips over the shaft, and locks in place as it cools.
Disclaimer: Tolerance values are representative of standard ISO/ANSI classes. For exact tolerance ranges at your specific nominal size, consult ISO 286 or the bearing manufacturer's mounting guide. Fit recommendations assume standard-clearance bearings. If using C3 or C4 clearance bearings, tighter shaft fits are acceptable.

Learn More

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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.

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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.

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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.

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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.

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