2Z is a bearing with a pressed steel shield on each side. The shield is a disc with a narrow labyrinth gap to the inner ring: nothing rubs, so friction stays low and the speed rating stays close to an open bearing. What a shield does not do is seal — fine dust, water and vapour pass the gap.
The shield is stamped into the outer ring groove and forms a narrow, usually L-shaped gap with the inner ring. Air has to turn a corner to get through, which stops chips, swarf and coarse grit. Because there is no rubbing surface, the bearing keeps almost all of its speed capability and adds little torque — which is why 2Z is the standard choice on motors and gearboxes.
2Z is the right answer whenever the bearing runs fast and the environment is dry.
A shield is a deflector, not a barrier. In fine abrasive dust — cement, carbon black, sandblasting, mineral processing — particles small enough to pass the gap act as lapping compound on the raceway and shorten life dramatically. In those environments the same bearing in 2RS lasts several times longer, even at reduced speed.
| Meaning | Pressed steel shield, both sides |
|---|---|
| Single-side version | Z (one shield) |
| Construction | Steel disc, labyrinth gap, no contact |
| Temperature range | −30 to +150 °C, limited by the grease |
| Speed rating | 85–95% of the open bearing |
| Protection | Coarse dust and mechanical debris only |
| Water | Not resistant — splash passes the gap |
| Relubrication | Not through the shield; some designs allow it via a groove |
| Brand equivalents | SKF Z/2Z · FAG ZR/2ZR · NSK ZZ · NTN ZZ · KOYO ZZ |
| Criterion | 2Z | 2RS | Open |
|---|---|---|---|
| Contact with inner ring | No | Yes | — |
| Coarse dust | Blocked | Blocked | Passes |
| Fine dust | Passes slowly | Blocked | Passes |
| Water splash | Passes | Blocked | Passes |
| Speed vs open | 85–95% | 60–70% | 100% |
| Temperature ceiling | Grease-limited (~150 °C) | 120 °C seal limit | Grease or oil |
| Relubrication | Possible in some designs | No | Yes |
| Typical position | Motor, gearbox, fan | Conveyor, pump, outdoor | Oil bath, spindle |
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Read →No seal — maximum speed, relubrication access
Read →The brand crosswalk for contact rubber seals
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Read →FKM and PTFE seals for 150–260 °C
Read →In practice yes. ZZ is the same double-shielded bearing written the way Japanese and Chinese catalogues usually write it; European catalogues write 2Z. Ordering either designation gets you a shielded bearing on both sides.
No. The labyrinth gap is open to splash and vapour. For splash resistance you need a contact seal (2RS) or a housed unit with a separate seal.
Only if the design provides a lubrication groove and holes, which most standard 2Z bearings do not. Otherwise the shield has to be removed, which defeats the purpose.
2RZ. It seals better than a shield against the fine dust that collects around fans, while keeping 80–90% of the speed rating. Use 2RS only if the motor is washed down and the speed allows it.
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