681-672 bearing: complete specifications & equivalents
The 681-672 is a ANSI ABMA 19.2 radial bearing sized 92.075 x 168.275 x 41.275 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 92.075 mm |
| Outer diameter D | 168.275 mm |
| Width B | 41.275 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 247 kN |
| Basic static load rating C0 | 340 kN |
| Limiting speed (mechanical) | 2100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3870 g |
| Manufacturer designation | NTN 4T-681/672 |
| 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 | 3.625 in |
|---|---|
| Outer diameter D | 6.625 in |
| Width B | 1.625 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 38.1 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) | 110 of 148 |
| Bore above smallest 4t-inch-series size | 79.375 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 681 | 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 681-672 model number is decoded
4T-681/672 is the NTN 4T catalogue entry for a 92.075×168.275×41.275 mm inch tapered roller bearing — an ABMA-dimensioned cone/cup set, not an ISO 355 metric bearing, even though the table quotes metric equivalents. Cone and cup of 4T-681/672 are separately stocked parts: a worn 672 cup can be replaced against the existing 681 cone, provided the new cup carries the identical reference — pairing across references changes the 41.275 mm assembled width and the rating. The 2.7 kN of dynamic capacity per millimetre of bore summarises the 247 kN rating over the 92.075 mm bore — sanity-check any interchange candidate against this ratio and the 41.275 mm T. The printed 247/340 kN ratings belong to the assembled 681+672 pair; a sibling row using the same cone with a different cup carries its own rating row because the raceway track shifts with the cup. A single-row tapered bearing reacts thrust in one direction only; 4T-681/672 is adjusted against a second bearing so the shaft is located in both directions.
Typical equipment & failure modes
Common applications
- paper-machine and calender roll supports
- off-highway and forestry machine axles
- marine winch and deck-machinery shafts
- crusher and screening-plant eccentric shafts
Known failure patterns
- cone-rib and roller large-end smearing when the adjusted pair runs with preload but starved lubricant film
- preload loss and noise after one bearing of the adjusted pair is replaced without resetting end play
- false brinelling on a stationary pair exposed to vibration during transport or standby
- cage fatigue when the pair runs continuously near the grease limiting speed without oil cooling
- indentation of the raceways by hard particles in an open, unsealed arrangement
Selection pitfalls — read before you substitute
- Mount the 92.075 mm cone by induction heating (max 120 °C) and the 168.275 mm cup with a press sleeve; at 3870 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 92.075 mm bore (168.275×41.275 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 681/672 reference at purchase.
- Grease packs must leave free volume inside the 41.275 mm-wide set; over-greasing a pair churning near the oil-band speed of 2,800 r/min raises temperature and destroys the setting.
- Inch and metric bores collide on paper — 92.075 mm is 3.625 in, not a round metric size; a metric bearing that seems 0.1 mm off will not seat on the inch shaft.
- Open 4T-681/672 sets have no seals: a hub or gearbox needs external sealing or the 2,100 r/min grease figure is meaningless once water reaches the cone rib.
- The 247/340 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-681/672; 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-681/672?
4T-681/672 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 92.075 mm bore (3.625 in), 168.275 mm outside diameter and 41.275 mm assembled width T (6.625 × 1.625 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 247 kN, C0 340 kN, grease limiting speed 2,100 r/min, oil speed 2,800 r/min, mass about 3870 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-681/672 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 681 cone or the 672 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 247/340 kN ratings change with the cup.
What is the difference between 4T-681/672 and a metric ISO 355 tapered bearing?
4T-681/672 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 92.075×168.275×41.275 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-681/672 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 681/672 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-681/672 list two speeds, 2,100 and 2,800 r/min?
The lower figure, 2,100 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-681/672 at 2,800 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.