1211 bearing: complete specifications & equivalents
The 1211 is a ISO 15 radial bearing sized 55 x 100 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 55 mm |
| Outer diameter D | 100 mm |
| Width B | 21 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 26.9 kN |
| Basic static load rating C0 | 10 kN |
| Fatigue load limit Pu | 0.4 kN |
| Limiting speed (mechanical) | 6000 rpm |
| Mass | 708 g |
| Manufacturer designation | 1211S |
| Standard | ISO 15 |
| Catalog version | CAT. No. 2203-3/E 2024 |
| Last verified | 2026-09-25 |
Source: catalog reference (CAT. No. 2203-3/E 2024) · extracted 2026-09-25
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (CAT. No. 2203-3/E 2024); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & 1200-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 0.827 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 22.5 mm |
| Smallest bore in 1200-series | 10 mm |
| Largest outer diameter in 1200-series | 200 mm |
| Width range across 1200-series | 9–38 mm |
| Bore position in 1200-series (smallest first) | 12 of 23 |
| Bore above smallest 1200-series size | 45 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 1211 model number is decoded
In the 1200-series (ISO 15 dimension series) the leading digits 12 mark a double-row self-aligning ball bearing and the last two digits encode the bore: 1211 carries bore code 11 = 55 mm. Outside diameter 100 mm and width 21 mm follow the ISO 15 general plan. The cylindrical bore fits directly on a machined shaft seat; a tapered-bore K variant is available for adapter-sleeve mounting. Two rows of balls run on a common sphered outer raceway, allowing the inner ring to pivot and compensate for shaft deflection or housing misalignment.
Typical equipment & failure modes
Common applications
- paper mill and processing equipment shafts
- industrial electric motor shafts
- pump and compressor drive shafts
- gearbox and speed reducer shafts
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- fretting corrosion on a loose shaft seat
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- Temperature rise and interference fits consume internal clearance on this 55 mm bore: a CN bearing on a tight, hot shaft can lose all residual clearance — size 1211 with C3 for those conditions.
- The 12xx light section at 55 mm bore uses a smaller 100 mm OD than a 1311; load ratings are lower, so do not replace a failed 13-series bearing with a 12-series without re-rating the load.
- The open 1211 has no lubricant retention: grease escapes and contaminants migrate straight into the 55×100×21 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Open bearings tolerate the highest speeds in the 1200-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 1211 units.
- A 55 mm bore listing showing the right d/D/B but no standard or precision-class reference may be a loose-tolerance import; measure bore/OD spread before fitting it to a machined shaft.
Frequently asked questions
What are the dimensions of a 1211 self-aligning ball bearing?
A 1211 self-aligning ball bearing has a 55 mm bore, 100 mm outer diameter and 21 mm width, per ISO 15 boundary dimensions. This is the cylindrical-bore version; a tapered-bore K variant is available for adapter-sleeve mounting.
How does the 1211 bore code work?
The last two digits of 1211 are bore code 11, giving 11 × 5 = 55 mm bore. The 100 mm outside diameter and 21 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the open suffix mean on 1211?
A bare 1211 designation means open: no shields or seals, normal CN radial clearance and P0 normal tolerance unless further suffixes are ordered. The application must supply and retain the lubrication.
How does the 1200 compare with other self-aligning series at the same 55 mm bore?
The 12xx is the light section: 100×21 mm with a 22.5 mm radial section at 55 mm bore — below 13/22/23 in load capacity, for light loads in compact spaces.
Reviewed & verified by the MPN Base engineering desk against source catalog CAT. No. 2203-3/E 2024 on 2026-09-25. Read our editorial & correction policy.