Rolling Bearing Radial Internal Clearance Classes

Bearing clearance codes describe the relative internal clearance before installation. This table shows the usual progression for common radial bearing classes. It intentionally gives no micrometer ranges: actual limits depend on bearing type, size, design, and manufacturer’s product table.

Radial bearing clearance class table

MECHANITEC / ENGINEERING REFERENCE

Rolling bearing radial internal clearance classes

Relative order and general meaning of common radial bearing internal-clearance classes.

1–5 of 5 matching rows (5 total)

Rolling bearing radial internal clearance classes — page 1 of 1
Radial clearance class	Relative to normal	Typical designation meaning
C2	Below normal	Smaller internal clearance than normal
CN / Normal	Reference class	Normal internal clearance; often unmarked depending on bearing system
C3	Above normal	Greater internal clearance than normal
C4	Above C3	Greater internal clearance than C3
C5	Above C4	Greater internal clearance than C4

Search and sort apply to all 5 rows. Print and CSV include only the 5 rows shown on this page.

How to read the class order

For the common radial-bearing series, clearance increases in the order C2, normal (often CN), C3, C4, and C5. C2 denotes less clearance than normal; C3 denotes more than normal; C4 is above C3; and C5 is above C4. Normal clearance may be unmarked depending on the maker’s designation system.

This is an ordering, not a universal numerical scale. A C3 bearing of one type or bore size should not be assumed to have the same micrometer range as a different bearing family or series. Manufacturers may also use distinct suffixes for non-interchangeable cylindrical roller bearings, miniature bearings, motor bearings, noise classes, or other product-specific requirements.

Why installed clearance differs

The radial play measured before mounting is not necessarily the clearance during operation. Fits can reduce clearance as the rings expand or contract; temperature differences between shaft, inner ring, outer ring, and housing can change it further. Shaft deflection, load, speed, lubrication, and assembly conditions also affect the final operating state.

A larger class is sometimes considered when interference fits or a hotter inner ring would reduce clearance. A smaller-than-normal class may be used in specific arrangements, but choosing a suffix from a rule of thumb can cause excessive preload or inadequate operating clearance. Use the bearing maker’s selection method and the exact tables for the bearing under consideration.

Selection checklist

Identify the complete bearing designation, product family, bore size, and clearance suffix.
Determine the shaft and housing fits and their expected effect on clearance.
Estimate ring temperatures and load conditions over the operating cycle.
Read the manufacturer’s range and measurement notes for that exact bearing type.
Confirm the resulting operating clearance and lubrication with the equipment design requirements.

Do not substitute this class-order table for a bearing dimension chart or a manufacturer’s clearance range. The bearing maker’s current product documentation governs when its designation differs from the general convention summarized here.

Source

The class order and general designation meanings are summarized from NSK’s guide to fits and internal clearance. NSK also documents distinct clearance codes for some bearing families and applications, which is why this reference remains qualitative.