Inner race joint gaps

When the inner race is assembled around a shaft, there shall be a small gap at the joint. The gaps at the joints, typically between 0.015” (0.4mm) and 0.025” (0.5mm) per side ensure contact between the bore of the inner race and the shaft. This is illustrated to the right.

Selection of internal bearing clearance

Cn represents the standard diametral clearance between the rollers and the outer race specified by the American Bearing Manufacturers Association (ABMA) and is usually adequate between 0°-212°F (minus 20°C to 100°C) and when the temperature difference between the shaft temperature and the housing temperature is less than 70°F (40°C). [T< 70°F (40°C)].

C2 clearance is less than standard and is used for reciprocating applications or when the shock loads and other conditions demand close clearance. It is limited to a temperature difference of 30°F (17°C) between shaft and housing temperature since high temperatures cause expansion of the bearing components. [T< 30°F (17°C)].

C3 clearance is greater than standard and is typically used when the difference between the shaft and bearing housing surface temperatures is between 70°F (40°C) and 130°F (72°C). [70°F< T < 130°F ]. [40°C< T < 72°C]

C5 is typically the greatest clearance that Cooper offers. It is used when the difference between the shaft and bearing housing surface temperatures is greater than 130°F (72°C). [T > 130°/ 72°C].

Bearings with C2 clearance will have higher capacity than similar bearings with C3 or C5 clearance. C3 reduces capacity by 5% and C5 by 10%. Cooper does not typically offer a C4 clearance.

For most industrial applications zero clearance is not desirable. Bearings will generate heat as they run, without clearance bearings bind and fail prematurely.