Boundary dimensions are standardised. Almost nothing else is. This is how to cross-reference a bearing without quietly changing the specification.
| What is standardised | Boundary dimensions (ISO 15) — bore, OD, width, chamfer |
|---|---|
| What is not | Clearance, cage, grease, seal design, precision, load rating, internal geometry |
| Biggest risk | Same size, different clearance or grease — invisible until the failure |
| Check 1 | Internal clearance (C-class) |
| Check 2 | Cage material and design |
| Check 3 | Seal or shield type and torque |
| Check 4 | Lubricant type, fill and temperature range |
| Check 5 | Dynamic and static load rating |
| Level | What matches | Risk | When it is acceptable |
|---|---|---|---|
| Dimensional | Boundary dimensions only | High — everything else may differ | Only for low-speed, low-consequence positions |
| Functional | Dimensions + clearance + seal + grease class | Moderate | Most industrial replacement |
| Exact | Dimensions + full suffix + rating + documentation | Low | Safety-critical, warranty, OEM service |
A C3 bearing in a C2 position runs loose and noisy; a CN bearing in a C3 position runs hot and fails early. Clearance is chosen from the fit, the temperature difference and the speed, and it is the single most common silent difference between two brands' “same” bearing.
A polyamide cage and a brass cage are not interchangeable at 150 °C, and a stamped steel cage is not interchangeable with a machined brass one in a high-vibration position. Cage material is often the first thing a cost-reduced equivalent changes.
2RS, 2RS1, 2RSH, 2RZ, DDU, LLU are all “sealed” and differ in contact pressure, torque and speed limit. A contact seal in a high-speed position overheats; a non-contact seal in a washdown position lets water in.
Grease type, fill percentage and base-oil viscosity decide life at temperature. Two bearings with identical dimensions can have grease rated for 120 °C and 180 °C respectively, with nothing on the box to say so.
A cost-reduced equivalent may have a lower dynamic rating through a thinner section or a different heat treatment. If the original selection was close to its limit, a 10% reduction is the difference between design life and a warranty claim.
Dimensionally yes; functionally, only if clearance, cage, seal and grease also match. That is four things that are not in the number “6205”, which is why the full designation matters.
Only if the original C3 was over-specified. C3 exists for a reason — temperature difference between inner and outer ring, interference fits, or heat from the process. Removing it closes the clearance.
Usually a stainless variant, but the letter is brand-specific. Suffix letters are not fully standardised, which is why cross-referencing needs the brand's own catalogue, not a generic decoder.
Ask for it in writing, with the dynamic and static figures. A supplier who cannot state the rating cannot support the substitution.
Send the BOM, the inspection plan or the failure photos. We will run through the same checklist and send back the gaps.