30208-NTN bearing: complete specifications & equivalents
The 30208-NTN is a ISO 355 radial bearing sized 40 x 80 x 19.75 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 40 mm |
| Outer diameter D | 80 mm |
| Width B | 19.75 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 68 kN |
| Basic static load rating C0 | 67 kN |
| Limiting speed (mechanical) | 4900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 431 g |
| Manufacturer designation | NTN 30208 |
| 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 | 1.575 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 0.778 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 20 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) | 8 of 37 |
| Bore above smallest 30200-series size | 25 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30208 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×80×19.75 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 30208-DF | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Model-number interchange per ISO 15; confirm dimensions, sealing and ratings in the supplier catalogue. |
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 30208-NTN model number is decoded
The NTN 2203E table prints 30208 in the standard-section 30200 family: 40 mm bore, 80 mm cup OD, 19.75 mm T, with a grease limiting speed of 4,900 r/min and an oil-lubricated ceiling of 6,600 r/min. NTN also quotes this bearing with its ISO 355 dimension-series abbreviation, 3DB, which is the maker-neutral cross-reference for the 40×80 mm envelope; 4T is NTN's own tapered-roller brand mark on the parts. A tapered roller bearing reacts combined radial and one-direction axial load; NTN mounts 30208 cone and cup separately and adjusts end play or preload against a second bearing, so the arrangement locates the shaft in both directions. Catalogue mass of the 30208 set is 431 g (0.017 lb cone + cup); abutment and shaft shoulder design must carry that mass square to the axis. After mounting check the contact pattern with marking blue: a pattern biased to the large or small roller end means the 40 mm pair is misadjusted and the 19.75 mm T set will edge-load in service.
Typical equipment & failure modes
Common applications
- industrial gearbox and speed-reducer shafts
- bevel and helical pinion drives with high thrust component
- pump and compressor drive shafts carrying combined load
- machine-tool gearbox and headstock shafts
Known failure patterns
- cup creep and housing fretting when the specified outer-ring press fit is not achieved
- rib scoring when axial load is carried beyond the cone rib capacity of the adjusted pair
- preload loss from racewear when one bearing of the paired set is replaced without re-adjusting end play
- cage fatigue when the pair is run continuously near the grease limiting speed without oil cooling
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Hub and pinion bearings of this 40 mm bore class are commonly adjusted in pairs; verify end play against the axle drawing and re-torque after bedding-in rather than trusting the initial preload on 30208.
- The standard-section 30200 family at 40 mm bore (80×19.75 mm assembled) carries more capacity than the lighter 320/329 sections but generates more preload heat; confirm oil availability before running near the 6,600 r/min oil ceiling.
- Do not confuse T (19.75 mm assembled width of cone + cup) with the cone width when drawing spacers; an abutment sized to T instead of the ring width leaves the cup unseated.
- Replacing one half of an adjusted pair without resetting end play negates the 19.75 mm T dimension logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- Do not confuse T (19.75 mm assembled width of cone + cup) with the cone width when drawing spacers; an abutment sized to T instead of the ring width leaves the cup unseated.
- The 68/67 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30208 (ISO 355 3DB); 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 30208?
30208 is a metric 4T tapered roller bearing to ISO 355: 40 mm bore, 80 mm outside diameter and 19.75 mm assembled width T (1.575 × 3.15 × 0.778 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 68 kN, C0 67 kN (2203E prints no Pu for this size), grease limiting speed 4,900 r/min, oil speed 6,600 r/min, mass about 431 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30208?
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 (30208); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30208 designation encode the 40 mm bore and what is 3DB?
last two digits 08 are the ISO bore code, ×5 = 40 mm (codes 00–03 use the 10/12/15/17 exception table). The 80 mm OD and 19.75 mm assembled T follow the ISO 355 dimension-series plan. 3DB 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 30208 list two speeds, 4,900 and 6,600 r/min?
The lower figure, 4,900 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30208 at 6,600 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30208 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.