619-612 bearing: complete specifications & equivalents
The 619-612 is a ANSI ABMA 19.2 radial bearing sized 50.8 x 120.65 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 | 50.8 mm |
| Outer diameter D | 120.65 mm |
| Width B | 41.275 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 190 kN |
| Basic static load rating C0 | 213 kN |
| Limiting speed (mechanical) | 3300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2300 g |
| Manufacturer designation | NTN 4T-619/612 |
| 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 | 4.75 in |
| Width B | 1.625 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 34.9 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 |
|---|---|---|---|
| 619 | 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 619-612 model number is decoded
For an inch shaft of 50.8 mm carrying combined radial and thrust load, NTN lists 4T-619/612, a single-row 4T tapered roller set of 190 kN C and 213 kN C0 inside the 120.65 mm OD cup. The 4T prefix is NTN's tapered roller quality mark stamped on both parts; it is a brand mark, not a size code, so cross-references quote 619/612 without it. Contact-angle geometry of the pure-numeric inch family gives 4T-619/612 its radial/axial load split — at 190/213 kN the static rating is about 1.12× C, typical of inch tapered sets proportioned for combined duty. Housing fitment sequence for 4T-619/612: press the 612 cup square into the 120.65 mm seat first, then bring the 619 cone (on its 50.8 mm shaft) into adjustment — the two references are separate engineering parts that happen to ship as one set. Running clearance of 4T-619/612 is set at mounting by axial displacement of cone or cup — the catalogue does not ship a preloaded set, so the drawing must state end play or preload.
Typical equipment & failure modes
Common applications
- agricultural tractor transmission and PTO shafts
- industrial gearboxes built to inch shafting
- construction-equipment pivot and wheel positions
- mining and quarry conveyor drive pulleys
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 damage from a mounting blow transmitted through the roller complement
- fretting corrosion on a loose cone seat that creeps under rotating 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-619/612.
- The pure-numeric inch family at 50.8 mm bore (120.65×41.275 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 619/612 reference at purchase.
- ABMA makes the 50.8×120.65 mm envelope interchangeable, not the ratings: NTN prints 190/213 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 41.275 mm T logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- Open 4T-619/612 sets have no seals: a hub or gearbox needs external sealing or the 3,300 r/min grease figure is meaningless once water reaches the cone rib.
- The 190/213 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-619/612; 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-619/612?
4T-619/612 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 50.8 mm bore (2 in), 120.65 mm outside diameter and 41.275 mm assembled width T (4.75 × 1.625 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 190 kN, C0 213 kN, grease limiting speed 3,300 r/min, oil speed 4,400 r/min, mass about 2300 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-619/612 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 619 cone or the 612 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 190/213 kN ratings change with the cup.
What is the difference between 4T-619/612 and a metric ISO 355 tapered bearing?
4T-619/612 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 50.8×120.65×41.275 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-619/612 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 619/612 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-619/612 list two speeds, 3,300 and 4,400 r/min?
The lower figure, 3,300 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-619/612 at 4,400 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.