1221 bearing: complete specifications & equivalents
The 1221 is a ISO 15 radial bearing sized 105 x 190 x 36 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 105 mm |
| Outer diameter D | 190 mm |
| Width B | 36 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 75 kN |
| Basic static load rating C0 | 32.5 kN |
| Fatigue load limit Pu | 1.3 kN |
| Limiting speed (mechanical) | 3000 rpm |
| Mass | 4430 g |
| Manufacturer designation | 1221S |
| 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 | 4.134 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.417 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 42.5 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) | 22 of 23 |
| Bore above smallest 1200-series size | 95 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 1221 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: 1221 carries bore code 21 = 105 mm. Outside diameter 190 mm and width 36 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
- hoist, winch and crane drums
- heavy conveyor drive shafts
- pulp, paper and steel mill machinery
- heavy industrial drive shafts
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- edge loading and stress concentration from excessive misalignment beyond the allowable angle
- raceway smearing under marginal lubrication at start-up
Selection pitfalls — read before you substitute
- Mount this 105 mm bore bearing by heating the inner ring (induction heater, max 120 °C) — never drive it home through the outer ring or balls, that brinells the raceways.
- The 12xx light section at 105 mm bore uses a smaller 190 mm OD than a 1321; load ratings are lower, so do not replace a failed 13-series bearing with a 12-series without re-rating the load.
- The open 1221 has no lubricant retention: grease escapes and contaminants migrate straight into the 105×190×36 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 1221 units.
- Do not use a self-aligning ball bearing where high radial rigidity is required — the sphered outer raceway allows more radial movement than a deep-groove or cylindrical roller bearing.
Frequently asked questions
What are the dimensions of a 1221 self-aligning ball bearing?
A 1221 self-aligning ball bearing has a 105 mm bore, 190 mm outer diameter and 36 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 1221 bore code work?
The last two digits of 1221 are bore code 21, giving 21 × 5 = 105 mm bore. The 190 mm outside diameter and 36 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the open suffix mean on 1221?
A bare 1221 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 105 mm bore?
The 12xx is the light section: 190×36 mm with a 42.5 mm radial section at 105 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.