1304K bearing: complete specifications & equivalents
The 1304K is a ISO 15 radial bearing sized 20 x 52 x 15 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 20 mm |
| Outer diameter D | 52 mm |
| Width B | 15 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 12.6 kN |
| Basic static load rating C0 | 3.35 kN |
| Fatigue load limit Pu | 0.14 kN |
| Limiting speed (mechanical) | 12000 rpm |
| Mass | 164 g |
| Manufacturer designation | 1304SK |
| 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 & 1300-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.591 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 16 mm |
| Smallest bore in 1300-series | 10 mm |
| Largest outer diameter in 1300-series | 240 mm |
| Width range across 1300-series | 11–50 mm |
| Bore position in 1300-series (smallest first) | 5 of 23 |
| Bore above smallest 1300-series size | 10 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 1304K model number is decoded
In the 1300-series (ISO 15 dimension series) the leading digits 13 mark a double-row self-aligning ball bearing and the last two digits encode the bore: 1304 carries bore code 04 = 20 mm. Outside diameter 52 mm and width 15 mm follow the ISO 15 general plan. The K suffix denotes a 1:12 tapered bore for mounting on an adapter sleeve or tapered shaft seat; the cylindrical-bore equivalent is 1304. 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
- centrifugal pump shafts
- small gearbox input/output shafts
- conveyor roller and pulley shafts
- agricultural equipment (harvesters, balers)
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- false brinelling from vibration while the shaft is stationary
- edge loading and stress concentration from excessive misalignment beyond the allowable angle
Selection pitfalls — read before you substitute
- At a 20 mm bore, a shaft-seat burr or an overtight setscrew can score the thin inner ring of 1304K; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
- The 13xx medium section at 20 mm bore gains rating through a larger 52 mm OD and 15 mm width; verify the housing accepts the larger envelope before substituting for a 1204.
- Tapered-bore 1304K requires a matching adapter sleeve (e.g. H2xx for small bores, H3xx for larger); verify the sleeve bore code matches the 20 mm shaft before ordering.
- The adapter sleeve adds length and a small radial step; check that the housing bore and shaft shoulder clear the sleeve nut and that the withdrawal nut is accessible for future dismounting.
- The self-aligning feature compensates for static misalignment and shaft deflection, not for poor initial alignment — always align shaft and housing as accurately as possible before fitting 1304K.
Frequently asked questions
What are the dimensions of a 1304K self-aligning ball bearing?
A 1304K self-aligning ball bearing has a 20 mm bore, 52 mm outer diameter and 15 mm width, per ISO 15 boundary dimensions. The K suffix indicates a 1:12 tapered bore for adapter-sleeve mounting; the cylindrical-bore version is 1304.
How does the 1304 bore code work?
The last two digits of 1304 are bore code 04, giving 04 × 5 = 20 mm bore. The 52 mm outside diameter and 15 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the K suffix mean on 1304K?
The K suffix denotes a 1:12 tapered bore for mounting with an adapter sleeve. The cylindrical-bore equivalent is 1304. Adapter sleeves are sold separately and must match the bore code.
How does the 1300 compare with other self-aligning series at the same 20 mm bore?
The 13xx is the medium section: 52×15 mm, 16.0 mm radial section at 20 mm bore, carrying more load than a 1204 but needing a larger housing bore.
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.