30348UTG bearing: complete specifications & equivalents
The 30348UTG is a ISO 355 radial bearing sized 240 x 500 x 105 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 240 mm |
| Outer diameter D | 500 mm |
| Width B | 105 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1900 kN |
| Basic static load rating C0 | 2000 kN |
| Fatigue load limit Pu | 165 kN |
| Limiting speed (mechanical) | 690 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 88300 g |
| Manufacturer designation | NTN 30348UTG |
| 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 | 9.449 in |
|---|---|
| Outer diameter D | 19.685 in |
| Width B | 4.134 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 130 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) | 32 of 32 |
| Bore above smallest 30300-series size | 225 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30348UTG | 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 30348UTG model number is decoded
30348UTG is the NTN 4T catalogue entry for a 240×500×105 mm metric tapered roller bearing — separable cone and cup, designed for combined radial and axial load as an individually adjusted bearing. Reading the designation: the leading five digits follow the ISO 355 metric plan (dimension family plus two-digit bore code), and 30348UTG resolves to 240 mm bore; the NTN factory mark 4T is stamped on cone and cup but is a brand mark, not a size code, so the catalogue sku is printed without it. Individually mounted, 30348UTG takes axial force in one direction only; two bearings are arranged face-to-face (X) or back-to-back (O) according to the moment stiffness and misalignment the shaft requires. Grease relubrication at 690 r/min limiting speed targets the rib contact; if the drive needs 990 r/min it must be arranged for oil lubrication with a defined flow to the large roller ends. Open 4T bearings need application seals; without them the grease at the cone rib of 30348UTG washes out and the rib/roller-end contact smears on the first wet or dusty shift.
Typical equipment & failure modes
Common applications
- heavy haul railway traction gearboxes
- large marine propulsion reduction gears
- cement-plant kiln and mill drive trains
- rolling-mill roll-neck and gearbox positions
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
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- indentation of the raceways by hard particles in unsealed open arrangements
Selection pitfalls — read before you substitute
- At 240 mm bore the 30348UTG set is adjusted with hydraulic nuts on large mill and wind positions; follow the drive-up angle/end-play procedure, because manual torque methods cannot control preload at the 1900 kN C level.
- 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 240 mm bore; do not swap to the lighter family without re-checking the 690 r/min grease limit and the thrust load split.
- Back-to-back and face-to-face arrangements react differently to shaft bending: pick the pair orientation for the moment load before locking the 240 mm shoulder geometry, because retrofitting flips the cups.
- Minimum load matters at high speed: an unloaded 30348UTG at a large fraction of 690 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded pair arrangements.
- Never fit the 240 mm cone by hammering the 500 mm cup: force for both press fits goes through the ring faces only, or brinell marks release as noise within the first running hours.
- The 1900/2000 kN ratings and 165 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30348UTG; 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 30348UTG?
30348UTG is a metric 4T tapered roller bearing to ISO 355: 240 mm bore, 500 mm outside diameter and 105 mm assembled width T (9.449 × 19.685 × 4.134 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1900 kN, C0 2000 kN, Pu 165 kN, grease limiting speed 690 r/min, oil speed 990 r/min, mass about 88300 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30348UTG?
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 (30348UTG); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30348UTG designation encode the 240 mm bore?
last two digits 48 are the ISO bore code, ×5 = 240 mm (codes 00–03 use the 10/12/15/17 exception table). The 500 mm OD and 105 mm assembled T follow the ISO 355 dimension-series plan.
Why does 30348UTG list two speeds, 690 and 990 r/min?
The lower figure, 690 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30348UTG at 990 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30348UTG mean?
Suffix reading on 30348UTG: the UTG suffix marks the ULTAGE specification for large NTN tapered rollers — upgraded material and internal design for longer life inside the unchanged ISO 355 envelope; 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.