What is bearing internal clearance?

Internal clearance is the total distance through which one bearing ring can be moved relative to the other in the radial direction (radial clearance) or axial direction (axial clearance). It is measured before mounting and is critical for proper bearing function.

When should I use C3 instead of CN (Normal) clearance?

C3 clearance (greater than Normal) is used when the bearing operates at elevated temperatures, has a tight interference fit on the shaft, or both. The extra clearance compensates for thermal expansion and fit-induced reduction. C3 is common for electric motors and pumps.

How does temperature affect bearing clearance?

Temperature causes thermal expansion of bearing components. The inner ring typically heats more than the outer ring, reducing radial clearance. For high-temperature applications, select a larger clearance class (C3, C4, or C5) to ensure adequate operating clearance.

How does interference fit affect bearing clearance?

An interference fit on the shaft expands the inner ring raceway, reducing radial clearance. Similarly, an interference fit in the housing compresses the outer ring raceway. The clearance reduction depends on the magnitude of interference, bearing dimensions, and material. This is why bearings with interference fits often require C3 or greater clearance.

Free Engineering Tool

Bearing Internal Clearance Calculator

Look up radial internal clearance for rolling bearings by bore diameter and clearance class per ISO 5753-1. Covers classes C2, CN, C3, C4, and C5.

ISO 5753-1 Radial Ball Bearings C2 – C5

Results

Radial Clearance Range

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Midpoint Clearance

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Clearance Class

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Bore Range Used

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All Clearance Classes for Selected Bore

Class	Min (μm)	Max (μm)	Midpoint (μm)

What is Internal Clearance?

Bearing internal clearance is the total distance through which one bearing ring can be moved relative to the other in the radial direction. It is defined by ISO 5753-1 for radial rolling bearings.

Clearance is specified as a range (minimum to maximum) for each bore diameter group and clearance class. The actual clearance of a manufactured bearing falls within this range.

Clearance Classes

Class	Description	Typical Use
C2	Less than Normal	Precision spindles, low noise applications
CN	Normal (default)	General-purpose machinery, standard conditions
C3	Greater than Normal	Electric motors, pumps, elevated temperature
C4	Greater than C3	Heavy interference fits, high temperature
C5	Greater than C4	Very high temperature, large interference fits

Effect of Fit and Temperature

The mounted (operating) clearance is always less than the unmounted clearance due to:

Interference fit — shaft fit expands the inner ring, reducing clearance
Temperature — inner ring typically runs hotter than outer ring

Practical Example

Example — Bearing 6210, bore Ø50 mm, class C3

Given: d = 50 mm, Clearance class = C3

From ISO 5753-1 table (bore range 40–50 mm):

C3 clearance: 20 – 43 μm

Midpoint: (20 + 43) / 2 = 31.5 μm

⚠️ Note: This table applies to radial ball bearings (deep groove, angular contact). Roller bearings, tapered roller bearings, and spherical roller bearings have different clearance tables per ISO 5753-1.

Bearing Internal Clearance Calculator | C2 CN C3 C4 C5 | ISO 5753

Published by admin on February 15, 2026 February 15, 2026