3780-3720-NTN bearing: complete specifications & equivalents
The 3780-3720-NTN is a ANSI ABMA 19.2 radial bearing sized 50.8 x 93.264 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 | 50.8 mm |
| Outer diameter D | 93.264 mm |
| Width B | 30.162 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 113 kN |
| Basic static load rating C0 | 134 kN |
| Limiting speed (mechanical) | 4000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 846 g |
| Manufacturer designation | NTN 4T-3780/3720 |
| 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 in |
|---|---|
| Outer diameter D | 3.672 in |
| Width B | 1.187 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 21.2 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) | 64 of 148 |
| Bore above smallest 4t-inch-series size | 38.099999999999994 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3780-3726 | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN cone 4T-3780 paired with a different cup (3726): cone interchangeable, cup differs — OD, assembled width T and ratings follow the cup. Verify the full cone/cup reference before substituting. |
| 3780-3732 | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN cone 4T-3780 paired with a different cup (3732): cone interchangeable, cup differs — OD, assembled width T and ratings follow the cup. Verify the full cone/cup reference before substituting. |
| 3780-3720 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 50.8×93.264×30.162 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
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 3780-3720-NTN model number is decoded
NTN supplies this 2 in (50.8 mm) shaft position as 4T-3780/3720: cone 3780, cup 3720, profiled rollers and a pressed-steel cage, rated 113 kN basic dynamic and 134 kN static. Reading the designation: 4T-3780/3720 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. Imperial cross-check for the drawing: 50.8×93.264×30.162 mm converts to 2 × 3.672 × 1.187 in; the ABMA envelope swaps with like-numbered inch parts but the 113/134 kN ratings are NTN-specific. Cup-side note for 3720: within the pure-numeric inch family tables the 3780 cone is listed against several cup options, and it is the cup that fixes the 93.264 mm OD and the 30.162 mm assembled width — quote the full 3780/3720 pair, never the cone alone. With a rotating shaft a k5/m5 cone seat and an easy-push cup seat are typical practice for 4T-3780/3720; reverse the fit logic when the cup rotates.
Typical equipment & failure modes
Common applications
- machine-tool headstocks on inch spindles
- pump and blower drive shafts with combined load
- truck and trailer axle hubs on inch-dimensioned axles
- agricultural tractor transmission and PTO shafts
Known failure patterns
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- flaking on one cone only when a bent shaft loads the O/X pair unevenly
- cup creep and housing fretting when the cup seat is cut too loose for the rotating load
- cage fatigue when the pair runs continuously near the grease limiting speed without oil cooling
- rolling-contact fatigue spalling after the catalogue L10 life at the actual combined load
Selection pitfalls — read before you substitute
- Hub and pinion positions of this 50.8 mm class are adjusted in pairs; verify end play against the axle or gearbox drawing and re-torque after bedding-in instead of trusting the first setting on 4T-3780/3720.
- The pure-numeric inch family at 50.8 mm bore (93.264×30.162 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 3780/3720 reference at purchase.
- Open 4T-3780/3720 sets have no seals: a hub or gearbox needs external sealing or the 4,000 r/min grease figure is meaningless once water reaches the cone rib.
- ABMA makes the 50.8×93.264 mm envelope interchangeable, not the ratings: NTN prints 113/134 kN for this execution and another make of the same number can differ in roller complement.
- Replacing one half of an adjusted pair without resetting end play negates the 30.162 mm T logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- The 113/134 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-3780/3720; 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-3780/3720?
4T-3780/3720 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 50.8 mm bore (2 in), 93.264 mm outside diameter and 30.162 mm assembled width T (3.672 × 1.187 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 113 kN, C0 134 kN, grease limiting speed 4,000 r/min, oil speed 5,300 r/min, mass about 846 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-3780/3720 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 3780 cone or the 3720 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 113/134 kN ratings change with the cup.
What is the difference between 4T-3780/3720 and a metric ISO 355 tapered bearing?
4T-3780/3720 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 50.8×93.264×30.162 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-3780/3720 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 3780/3720 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-3780/3720 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 4T-3780/3720 at 5,300 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.