C2 is one group tighter than normal. It suits bearings with a light interference fit, modest temperature rise and a requirement for low noise or accurate running — small motors, instruments, encoders and lightly loaded spindles. It is the wrong choice wherever the shaft will grow relative to the housing.
Less internal play means the rolling elements stay in contact with both raceways over a larger part of the load zone. Vibration at low load drops, running accuracy improves and the bearing is quieter at low speed. In a small fan motor or an encoder, that is the difference between an acceptable and an unacceptable product.
Clearance is consumed twice: once by the interference fit and once by the temperature difference between the inner and outer ring. C2 assumes both are small. Fit the same bearing with a heavier press fit, or run it at 90 °C in a housing that stays at 50 °C, and the residual clearance goes to zero. The symptoms are a hot bearing, a whining tone and short grease life — all of which get blamed on the grease.
| Relative to CN | One group tighter |
|---|---|
| Typical fits | Light interference or transition fit on the shaft |
| Temperature rise | Small — up to about 40 °C above ambient |
| Effect | Lower noise, better running accuracy, less axial play |
| Risk | Preload if the fit is heavier than designed |
| Typical use | Small motors, instruments, encoders, small fans |
| Availability | Catalogue item in small and medium sizes |
| Criterion | C2 | CN | C3 |
|---|---|---|---|
| Relative clearance | Tight | Normal | Loose |
| Fit assumed | Light | Normal | Medium to heavy |
| Temperature rise assumed | Small | Moderate | Large |
| Noise at low speed | Best | Good | Slightly higher |
| Heat tolerance | Lowest | Moderate | Highest |
| Typical use | Instrument, small motor | General engineering | Motor, fan, pump |
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Read →When the fit is light, the temperature rise is small and low noise or running accuracy is a requirement — typically small motors and instruments. In doubt, CN is safer.
Only if the clearance closes. Under the conditions it was designed for, C2 runs cooler because there is less element movement. Under a heavier fit it runs hotter than CN.
Rarely. Above about 80 mm bore, C2 is a special order and CN or C3 is normally stocked.
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