3994-3920 bearing: complete specifications & equivalents
The 3994-3920 is a ANSI ABMA 19.2 radial bearing sized 66.675 x 112.712 x 30.162 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 66.675 mm |
| Outer diameter D | 112.712 mm |
| Width B | 30.162 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 132 kN |
| Basic static load rating C0 | 174 kN |
| Limiting speed (mechanical) | 3200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1180 g |
| Manufacturer designation | NTN 4T-3994/3920 |
| 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 | 2.625 in |
|---|---|
| Outer diameter D | 4.437 in |
| Width B | 1.187 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 23 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) | 84 of 148 |
| Bore above smallest 4t-inch-series size | 53.974999999999994 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3994 | 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 3994-3920 model number is decoded
4T-3994/3920 is the NTN 4T catalogue entry for a 66.675×112.712×30.162 mm inch tapered roller bearing — an ABMA-dimensioned cone/cup set, not an ISO 355 metric bearing, even though the table quotes metric equivalents. Letter prefixes inherited from the inch convention mark the load family: LM reads as light-medium, HM as heavy-medium, LL as extra-light, J-prefixed codes as metric-envelope families — 3994 sits in the pure-numeric inch family. Grease relubrication at the 3,200 r/min limiting speed targets the cone-rib contact; sustaining 4,300 r/min needs an oil supply directed at the large roller ends. The printed 132/174 kN ratings belong to the assembled 3994+3920 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. The rollers run with their large ends against the cone's guide rib; lubricant must reach that rib face of 4T-3994/3920, not only the raceway, or the pair smears on the first overloaded start.
Typical equipment & failure modes
Common applications
- off-highway and forestry machine axles
- marine winch and deck-machinery shafts
- crusher and screening-plant eccentric shafts
- heavy truck and bus drive-axle differentials
Known failure patterns
- cone-rib and roller large-end smearing when the adjusted pair runs with preload but starved lubricant film
- 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 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 66.675 mm cone by induction heating (max 120 °C) and the 112.712 mm cup with a press sleeve; at 1180 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 66.675 mm bore (112.712×30.162 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 3994/3920 reference at purchase.
- An unloaded 4T-3994/3920 near 3,200 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded high-speed pairs.
- Do not confuse T (30.162 mm, the assembled cone-plus-cup width) with the cone width when drawing spacers; an abutment sized to T leaves the cup unseated.
- An unloaded 4T-3994/3920 near 3,200 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded high-speed pairs.
- The 132/174 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-3994/3920; 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-3994/3920?
4T-3994/3920 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 66.675 mm bore (2.625 in), 112.712 mm outside diameter and 30.162 mm assembled width T (4.437 × 1.187 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 132 kN, C0 174 kN, grease limiting speed 3,200 r/min, oil speed 4,300 r/min, mass about 1180 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-3994/3920 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 3994 cone or the 3920 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 132/174 kN ratings change with the cup.
What is the difference between 4T-3994/3920 and a metric ISO 355 tapered bearing?
4T-3994/3920 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 66.675×112.712×30.162 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-3994/3920 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 3994/3920 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-3994/3920 list two speeds, 3,200 and 4,300 r/min?
The lower figure, 3,200 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-3994/3920 at 4,300 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.