30309-NTN bearing: complete specifications & equivalents
The 30309-NTN is a ISO 355 radial bearing sized 45 x 100 x 27.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 45 mm |
| Outer diameter D | 100 mm |
| Width B | 27.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 123 kN |
| Basic static load rating C0 | 126 kN |
| Limiting speed (mechanical) | 4000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1010 g |
| Manufacturer designation | NTN 30309 |
| 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 | 1.772 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 1.073 in |
| ISO bore code | 09 |
| Radial section height (D−d)/2 | 27.5 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) | 8 of 32 |
| Bore above smallest 30300-series size | 30 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30309 | 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. |
| 30309-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 30309-NTN model number is decoded
30309 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. Digit by digit, the bare number identifies the large-OD 30300 family with the steeper contact angle and a bore code resolving to 45 mm; 100 mm OD and 27.25 mm assembled T are the matching ISO 355 boundary dimensions shared with other makers of the same dimension series. 2203E lists two speed ceilings for 30309: 4,000 r/min with grease lubrication (the limiting speed) and 5,300 r/min with oil, the higher oil value reflecting better heat removal from the cone rib. The 27.5 mm section height over the 45 mm bore positions the load centre; axial location of the pair depends on that contact line, so spacer faces must be square within the P0 tolerance of the bearing. After mounting check the contact pattern with marking blue: a pattern biased to the large or small roller end means the 45 mm pair is misadjusted and the 27.25 mm T set will edge-load in service.
Typical equipment & failure modes
Common applications
- pump and compressor drive shafts carrying combined load
- machine-tool gearbox and headstock shafts
- axle final-drive and differential positions
- construction-equipment wheel and pivot hubs
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 damage from a mounting blow delivered through the roller complement instead of the ring face
- rolling-contact fatigue after the catalogue L10 life at the actual combined load
Selection pitfalls — read before you substitute
- Hub and pinion bearings of this 45 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 30309.
- 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 45 mm bore; do not swap to the lighter family without re-checking the 4,000 r/min grease limit and the thrust load split.
- Do not confuse T (27.25 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.
- On slash-size and T-code bearings confirm the full code on both cone and cup before fitting: the 45 mm bore alone does not identify the cup, and a mismatched cone/cup set has no catalogue rating.
- Grease packs must leave free volume in the 27.25 mm-wide set; over-greasing a paired bearing churning at the 5,300 r/min oil-band speed raises temperature and destroys the preload setting.
- The 123/126 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30309 (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 30309?
30309 is a metric 4T tapered roller bearing to ISO 355: 45 mm bore, 100 mm outside diameter and 27.25 mm assembled width T (1.772 × 3.937 × 1.073 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 123 kN, C0 126 kN (2203E prints no Pu for this size), grease limiting speed 4,000 r/min, oil speed 5,300 r/min, mass about 1010 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30309?
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 (30309); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30309 designation encode the 45 mm bore and what is 2FB?
last two digits 09 are the ISO bore code, ×5 = 45 mm (codes 00–03 use the 10/12/15/17 exception table). The 100 mm OD and 27.25 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 30309 list two speeds, 4,000 and 5,300 r/min?
The lower figure, 4,000 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30309 at 5,300 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30309 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.