30304A bearing: complete specifications & equivalents
The 30304A is a ISO 355 radial bearing sized 20 x 52 x 16.25 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 | 16.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 39 kN |
| Basic static load rating C0 | 34 kN |
| Limiting speed (mechanical) | 8000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 172 g |
| Manufacturer designation | NTN 30304A |
| Standard | ISO 355 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); 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 & 30300-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.64 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 16 mm |
| Smallest bore in 30300-series | 15 mm |
| Largest outer diameter in 30300-series | 500 mm |
| Width range across 30300-series | 14.25–105 mm |
| Bore position in 30300-series (smallest first) | 3 of 32 |
| Bore above smallest 30300-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30304A | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 30304A model number is decoded
30304A belongs to the NTN metric 4T tapered roller range (large-OD 30300 family with the steeper contact angle); the open bearing leaves sealing to the application and is normally ordered and mounted as an adjustable matched pair. NTN also quotes this bearing with its ISO 355 dimension-series abbreviation, 2FB, which is the maker-neutral cross-reference for the 20×52 mm envelope; 4T is NTN's own tapered-roller brand mark on the parts. NTN adjusts these bearings by cup or cone position rather than shipping a preloaded set; the mounting drawing must state end play or preload for 30304A, since running clearance is set during assembly. Speed planning uses both catalogue columns: grease 8,000 r/min is the cage/rib mechanical ceiling for 30304A, oil 11,000 r/min is available with circulating oil — a 3,000 r/min margin at this size. With a rotating shaft a k5/m5 shaft seat and a press-fit cup are typical catalogue practice for 30304A; reverse the logic if the cup rotates, and re-verify against load direction and magnitude.
Typical equipment & failure modes
Common applications
- small conveyor pulley shafts
- steering-knuckle and kingpin positions
- small automotive wheel hubs and trailer axles
- light-vehicle differential and pinion shafts
Known failure patterns
- cone-raceway spalling at the large rib when preload is set too high for the lubricant film
- flaking on one cone only when a back-to-back / face-to-face pair is loaded unevenly by a bent shaft
- smearing on the roller large ends and cone rib after a dry start with preload but no oil film
- cage damage from a mounting blow delivered through the roller complement instead of the ring face
- indentation of the raceways by hard particles in unsealed open arrangements
Selection pitfalls — read before you substitute
- At 20 mm bore the thin section and small rollers are adjustment-sensitive: a quarter-turn of the locknut moves end play by more than on large bearings, so set the 30304A pair with a dial indicator rather than by feel.
- The steeper contact angle of the large-OD 30300 family with the steeper contact angle raises axial capacity but lowers the speed ceiling against a 302/322 bearing at 20 mm bore; do not swap to the lighter family without re-checking the 8,000 r/min grease limit and the thrust load split.
- ISO 355 makes the 20×52 mm envelope interchangeable but not the ratings: NTN prints 39/34 kN for this execution, and a cheaper same-number part can differ in roller complement and steel.
- Open 30304A units have no seals: a wheel-hub or gearbox application needs external sealing or the 8,000 r/min grease figure is meaningless once water reaches the cone rib.
- On slash-size and T-code bearings confirm the full code on both cone and cup before fitting: the 20 mm bore alone does not identify the cup, and a mismatched cone/cup set has no catalogue rating.
- The 39/34 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30304A (ISO 355 2FB); internal geometry legitimately differs between manufacturers, so re-verify ratings, adjustment and suffix before substituting another make on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 30304A?
30304A is a metric 4T tapered roller bearing to ISO 355: 20 mm bore, 52 mm outside diameter and 16.25 mm assembled width T (0.787 × 2.047 × 0.64 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 39 kN, C0 34 kN (2203E prints no Pu for this size), grease limiting speed 8,000 r/min, oil speed 11,000 r/min, mass about 172 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30304A?
4T is NTN's tapered roller bearing brand mark, stamped on the cone and cup in the factory. It identifies the NTN 4T programme and is not a dimension, so the catalogue and this page list the bare ISO 355 number (30304A); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30304A designation encode the 20 mm bore and what is 2FB?
last two digits 04 are the ISO bore code, ×5 = 20 mm (codes 00–03 use the 10/12/15/17 exception table). The 52 mm OD and 16.25 mm assembled T follow the ISO 355 dimension-series plan. 2FB is the maker-neutral ISO 355 abbreviation for this dimension series (the same code other manufacturers print); 4T is NTN's own brand mark.
Why does 30304A list two speeds, 8,000 and 11,000 r/min?
The lower figure, 8,000 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30304A at 11,000 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30304A mean?
Suffix reading on 30304A: the trailing A/C/D (or E1) letter marks an NTN contact-angle or internal-design revision of the base number, not a seal or clearance code; the suffix is part of the order number and the variants are not interchangeable articles.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.