34301-34478 bearing: complete specifications & equivalents
The 34301-34478 is a ANSI ABMA 19.2 radial bearing sized 76.2 x 121.442 x 24.608 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 76.2 mm |
| Outer diameter D | 121.442 mm |
| Width B | 24.608 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 101 kN |
| Basic static load rating C0 | 127 kN |
| Limiting speed (mechanical) | 2900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 976 g |
| Manufacturer designation | NTN 4T-34301/34478 |
| Standard | ANSI ABMA 19.2 |
| Catalog version | NTN 2203E 2026-09-25 |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN 2203E 2026-09-25) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN 2203E 2026-09-25); 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 & 4t-inch-series range
| Bore d | 3 in |
|---|---|
| Outer diameter D | 4.781 in |
| Width B | 0.969 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 22.6 mm |
| Smallest bore in 4t-inch-series | 12.7 mm |
| Largest outer diameter in 4t-inch-series | 260 mm |
| Width range across 4t-inch-series | 10.998–77.788 mm |
| Bore position in 4t-inch-series (smallest first) | 94 of 148 |
| Bore above smallest 4t-inch-series size | 63.5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 34301 | 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 34301-34478 model number is decoded
4T-34301/34478 belongs to the NTN inch 4T tapered roller range (pure-numeric inch family); cone and cup are ordered by their own references and are individually interchangeable with like-numbered parts. Reading the designation: 4T-34301/34478 follows the ABMA inch convention — the number before the slash is the cone (inner ring with roller set and cage), the number after the slash is the cup (outer ring), and the pure-numeric inch family lettering ties the pair to its boundary plan. Grease relubrication at the 2,900 r/min limiting speed targets the cone-rib contact; sustaining 3,800 r/min needs an oil supply directed at the large roller ends. Cup-side note for 34478: within the pure-numeric inch family tables the 34301 cone is listed against several cup options, and it is the cup that fixes the 121.442 mm OD and the 24.608 mm assembled width — quote the full 34301/34478 pair, never the cone alone. After bedding-in, re-check the end play of the adjusted 4T-34301/34478 pair — initial seating of the ring faces relaxes the setting slightly.
Typical equipment & failure modes
Common applications
- large conveyor head pulleys in bulk-handling plant
- paper-machine and calender roll supports
- off-highway and forestry machine axles
- marine winch and deck-machinery shafts
Known failure patterns
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- cup creep and housing fretting when the cup seat is cut too loose for the rotating load
- flaking on one cone only when a bent shaft loads the O/X pair unevenly
- cage damage from a mounting blow transmitted through the roller complement
- brinell marks on cone and cup raceways from impact during handling or hammer fitting
Selection pitfalls — read before you substitute
- Mount the 76.2 mm cone by induction heating (max 120 °C) and the 121.442 mm cup with a press sleeve; at 976 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 76.2 mm bore (121.442×24.608 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 34301/34478 reference at purchase.
- Never drive the 121.442 mm cup home through the rollers: fitting force goes through the ring faces only, or brinell marks release as noise within the first running hours.
- ABMA makes the 76.2×121.442 mm envelope interchangeable, not the ratings: NTN prints 101/127 kN for this execution and another make of the same number can differ in roller complement.
- An unloaded 4T-34301/34478 near 2,900 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded high-speed pairs.
- The 101/127 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-34301/34478; internal geometry legitimately differs between inch-series makers, so re-verify ratings, adjustment and the exact cone/cup references before substituting another brand on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 4T-34301/34478?
4T-34301/34478 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 76.2 mm bore (3 in), 121.442 mm outside diameter and 24.608 mm assembled width T (4.781 × 0.969 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 101 kN, C0 127 kN, grease limiting speed 2,900 r/min, oil speed 3,800 r/min, mass about 976 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-34301/34478 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 34301 cone or the 34478 cup can be replaced by an identical reference from NTN or another ABMA-dimensioned maker. Pairing the cone with a different cup reference is a different catalogue row: OD, assembled T and the 101/127 kN ratings change with the cup.
What is the difference between 4T-34301/34478 and a metric ISO 355 tapered bearing?
4T-34301/34478 follows the ABMA inch boundary plan with cone/cup references; ISO 355 bearings use metric dimension-series numbers (302, 322, …). Even where a metric size looks close to 76.2×121.442×24.608 mm, the envelopes and contact angles differ — the two systems are not drop-in interchangeable; check every boundary value before substituting.
What does the 4T prefix on 4T-34301/34478 mean?
4T is NTN's tapered roller bearing quality mark, stamped on cone and cup in the factory. It identifies NTN's 4T programme and is not a dimension or variant code, so interchange lists quote the bare 34301/34478 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-34301/34478 list two speeds, 2,900 and 3,800 r/min?
The lower figure, 2,900 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 4T-34301/34478 at 3,800 r/min because oil removes rib-contact heat better. Real limits still depend on pair adjustment, oil flow and cooling.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN 2203E 2026-09-25 on 2026-10-01. Read our editorial & correction policy.