18790-18724 bearing: complete specifications & equivalents
The 18790-18724 is a ANSI ABMA 19.2 radial bearing sized 50.8 x 88.9 x 17.462 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 | 88.9 mm |
| Width B | 17.462 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 55 kN |
| Basic static load rating C0 | 65 kN |
| Limiting speed (mechanical) | 4200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 431 g |
| Manufacturer designation | NTN 4T-18790/18724 |
| 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 | 3.5 in |
| Width B | 0.687 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 19.1 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) | 64 of 148 |
| Bore above smallest 4t-inch-series size | 38.099999999999994 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 18790-18720-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN cone 4T-18790 paired with a different cup (18720): cone interchangeable, cup differs — OD, assembled width T and ratings follow the cup. Verify the full cone/cup reference before substituting. |
| 18790-18720 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Model-number interchange per ISO 15; confirm dimensions, sealing and ratings in the supplier catalogue. |
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 18790-18724 model number is decoded
4T-18790/18724 is an NTN inch-series single-row tapered roller bearing: a separable cone-and-cup pair on the ABMA inch boundary plan, 50.8×88.9×17.462 mm (assembled width T), for a shaft of about 50.8 mm (2 in). 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 — 18790 sits in the pure-numeric inch family. Imperial cross-check for the drawing: 50.8×88.9×17.462 mm converts to 2 × 3.5 × 0.687 in; the ABMA envelope swaps with like-numbered inch parts but the 55/65 kN ratings are NTN-specific. Cup-side note for 18724: within the pure-numeric inch family tables the 18790 cone is listed against several cup options, and it is the cup that fixes the 88.9 mm OD and the 17.462 mm assembled width — quote the full 18790/18724 pair, never the cone alone. Minimum load matters at speed: an unloaded 4T-18790/18724 run near 4,200 r/min lets the rollers skid; lightly spring-preload high-speed pair arrangements.
Typical equipment & failure modes
Common applications
- pump and blower drive shafts with combined load
- truck and trailer axle hubs on inch-dimensioned axles
- agricultural tractor transmission and PTO shafts
- industrial gearboxes built to inch shafting
Known failure patterns
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- false brinelling on a stationary pair exposed to vibration during transport or standby
- preload loss and noise after one bearing of the adjusted pair is replaced without resetting end play
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- brinell marks on cone and cup raceways from impact during handling or hammer fitting
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-18790/18724.
- The pure-numeric inch family at 50.8 mm bore (88.9×17.462 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 18790/18724 reference at purchase.
- Open 4T-18790/18724 sets have no seals: a hub or gearbox needs external sealing or the 4,200 r/min grease figure is meaningless once water reaches the cone rib.
- Quote the full 18790/18724 pair at ordering: the 18790 cone also ships against sibling cups, and a cup from another reference changes the 17.462 mm assembled width and the rating.
- ABMA makes the 50.8×88.9 mm envelope interchangeable, not the ratings: NTN prints 55/65 kN for this execution and another make of the same number can differ in roller complement.
- The 55/65 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-18790/18724; 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-18790/18724?
4T-18790/18724 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 50.8 mm bore (2 in), 88.9 mm outside diameter and 17.462 mm assembled width T (3.5 × 0.687 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 55 kN, C0 65 kN, grease limiting speed 4,200 r/min, oil speed 5,600 r/min, mass about 431 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-18790/18724 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 18790 cone or the 18724 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 55/65 kN ratings change with the cup.
What is the difference between 4T-18790/18724 and a metric ISO 355 tapered bearing?
4T-18790/18724 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 50.8×88.9×17.462 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-18790/18724 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 18790/18724 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-18790/18724 list two speeds, 4,200 and 5,600 r/min?
The lower figure, 4,200 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-18790/18724 at 5,600 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.