30204-NTN bearing: complete specifications & equivalents
The 30204-NTN is a ISO 355 radial bearing sized 20 x 47 x 15.25 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 | 47 mm |
| Width B | 15.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 31 kN |
| Basic static load rating C0 | 28.7 kN |
| Limiting speed (mechanical) | 8800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 124 g |
| Manufacturer designation | NTN 30204 |
| 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 & 30200-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.85 in |
| Width B | 0.6 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 13.5 mm |
| Smallest bore in 30200-series | 15 mm |
| Largest outer diameter in 30200-series | 580 mm |
| Width range across 30200-series | 11.75–104 mm |
| Bore position in 30200-series (smallest first) | 3 of 37 |
| Bore above smallest 30200-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30204 | SKF | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
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 30204-NTN model number is decoded
The NTN 2203E table prints 30204 in the standard-section 30200 family: 20 mm bore, 47 mm cup OD, 15.25 mm T, with a grease limiting speed of 8,800 r/min and an oil-lubricated ceiling of 12,000 r/min. NTN also quotes this bearing with its ISO 355 dimension-series abbreviation, 2DB, which is the maker-neutral cross-reference for the 20×47 mm envelope; 4T is NTN's own tapered-roller brand mark on the parts. NTN grades 4T metric bearings as open bearings without integral seals; at 20 mm bore the application supplies the seals and the grease fill or oil supply to the 2DB ISO 355 assembly. Grease relubrication at 8,800 r/min limiting speed targets the rib contact; if the drive needs 12,000 r/min it must be arranged for oil lubrication with a defined flow to the large roller ends. Fillet radii must clear the ring chamfers of the 47 mm cup and 20 mm cone; use undercut shoulders so the rings seat fully rather than bridging on a shaft radius.
Typical equipment & failure modes
Common applications
- steering-knuckle and kingpin positions
- small automotive wheel hubs and trailer axles
- light-vehicle differential and pinion shafts
- agricultural implement hubs and ground-tool drives
Known failure patterns
- cone-raceway spalling at the large rib when preload is set too high for the lubricant film
- preload loss from racewear when one bearing of the paired set is replaced without re-adjusting end play
- rib scoring when axial load is carried beyond the cone rib capacity of the adjusted pair
- cage fatigue when the pair is run continuously near the grease limiting speed without oil cooling
- brinell marks on cone and cup raceways from impact during handling or hammering during fitting
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 30204 pair with a dial indicator rather than by feel.
- The standard-section 30200 family at 20 mm bore (47×15.25 mm assembled) carries more capacity than the lighter 320/329 sections but generates more preload heat; confirm oil availability before running near the 12,000 r/min oil ceiling.
- Replacing one half of an adjusted pair without resetting end play negates the 15.25 mm T dimension logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- Open 30204 units have no seals: a wheel-hub or gearbox application needs external sealing or the 8,800 r/min grease figure is meaningless once water reaches the cone rib.
- The 13.5 mm section leaves little room for an oversized shaft fillet; check the mounting-chamfer table for 30204 or the ring will bottom out on the radius instead of the shoulder face.
- The 31/28.7 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30204 (ISO 355 2DB); 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 30204?
30204 is a metric 4T tapered roller bearing to ISO 355: 20 mm bore, 47 mm outside diameter and 15.25 mm assembled width T (0.787 × 1.85 × 0.6 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 31 kN, C0 28.7 kN (2203E prints no Pu for this size), grease limiting speed 8,800 r/min, oil speed 12,000 r/min, mass about 124 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30204?
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 (30204); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30204 designation encode the 20 mm bore and what is 2DB?
last two digits 04 are the ISO bore code, ×5 = 20 mm (codes 00–03 use the 10/12/15/17 exception table). The 47 mm OD and 15.25 mm assembled T follow the ISO 355 dimension-series plan. 2DB 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 30204 list two speeds, 8,800 and 12,000 r/min?
The lower figure, 8,800 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30204 at 12,000 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30204 mean?
It is the basic open 4T execution — steel cage, adjusted mounting, no seal or feature suffix. NTN uses U for the uprated design, UTG for ULTAGE large-bearing specs, X for the ISO boundary section, and C/CA/D/A for contact-angle or internal-design variants; all are separate order numbers.
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.