An open bearing carries no suffix for sealing because it has none: the rolling elements and cage are exposed on both sides. It is the fastest, coolest and cheapest version of any given bearing, and it is the only version that can be relubricated or fed oil continuously — which is why it is standard inside gearboxes, spindles and oil-circulated machinery.
Any machine that already has a sealed housing and a lubrication system should use open bearings. Adding a seal to a bearing inside an oil-filled gearbox only traps heat and prevents the oil from reaching the raceway.
The bearing no longer protects itself. That responsibility moves to the housing seal, the breather and the lubricant maintenance plan. If any of those is missing, an open bearing will fail faster than a sealed one, and it will fail by contamination rather than by fatigue — usually within weeks in a dirty plant.
Most open bearings leave the factory with a preservative oil, not a service grease. They must be lubricated at assembly with the grade and fill the application calls for. Fitting one dry, or assuming it arrives ready to run, is one of the most common assembly errors we see.
| Meaning | No seal, no shield |
|---|---|
| Speed rating | 100% — the reference figure for the size |
| Lubrication | Oil bath, circulation, jet, mist, or grease via a line |
| Relubrication | Yes, continuously or at service intervals |
| Protection | None — relies entirely on the housing |
| Temperature | Limited by lubricant and cage, not by a seal |
| Cost | The lowest of the four versions |
| Not suitable for | Outdoor, dusty, washdown or sealed-for-life positions |
| Criterion | Open | 2Z shielded | 2RS sealed |
|---|---|---|---|
| Speed | 100% | 85–95% | 60–70% |
| Lubricant supply | Machine (oil or grease line) | Factory fill, limited relub | Factory fill, sealed for life |
| Relubrication | Yes | Sometimes | No |
| Housing seal required | Yes | Partly | No |
| Contamination tolerance | None | Coarse dust | Dust and splash |
| Heat rejection | Best | Good | Poorest |
| Typical position | Gearbox, spindle, oil circuit | Motor, fan | Conveyor, outdoor, pump |
Rubber contact seal on both sides — maximum protection
Read →Steel shield on both sides — high speed, coarse dust only
Read →Non-contact rubber seal — shield friction, better sealing
Read →The brand crosswalk for contact rubber seals
Read →SKF's reinforced contact seal for larger bores
Read →FKM and PTFE seals for 150–260 °C
Read →No. They are protected with a preservative coating only. They must be greased or oiled at assembly with the grade specified for the application.
Only inside a housing that is itself sealed against weather. An unprotected open bearing outdoors will ingest water and dust and fail quickly.
Not by adding seals — a seal kit is not available for a standard open bearing. Buy the sealed version; the boundary dimensions are identical.
Because nothing rubs. The speed limit of a sealed bearing is set by the seal lip temperature, while an open bearing is limited by cage strength, lubricant and centrifugal load on the rolling elements.
Send the designation, the three dimensions and the quantity — we reply with price, brand options and lead time within 30 minutes on working days.