749A-742-NTN bearing: complete specifications & equivalents
The 749A-742-NTN is a ANSI ABMA 19.2 radial bearing sized 82.55 x 150.089 x 44.45 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 82.55 mm |
| Outer diameter D | 150.089 mm |
| Width B | 44.45 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 289 kN |
| Basic static load rating C0 | 360 kN |
| Limiting speed (mechanical) | 2400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3370 g |
| Manufacturer designation | NTN 4T-749A/742 |
| 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 | 3.25 in |
|---|---|
| Outer diameter D | 5.909 in |
| Width B | 1.75 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 33.8 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) | 99 of 148 |
| Bore above smallest 4t-inch-series size | 69.85 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 749A-742 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 82.55×150.089×44.45 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 749A-742-NTN model number is decoded
4T-749A/742 is an NTN inch-series single-row tapered roller bearing: a separable cone-and-cup pair on the ABMA inch boundary plan, 82.55×150.089×44.45 mm (assembled width T), for a shaft of about 82.55 mm (3.25 in). Cone and cup of 4T-749A/742 are separately stocked parts: a worn 742 cup can be replaced against the existing 749A cone, provided the new cup carries the identical reference — pairing across references changes the 44.45 mm assembled width and the rating. Two single-row inch sets are normally mounted as an adjusted O or X pair; the 44.45 mm T of each 4T-749A/742 enters the spacer calculation, so the tolerance on assembled width matters as much as the bore fit. Housing fitment sequence for 4T-749A/742: press the 742 cup square into the 150.089 mm seat first, then bring the 749A cone (on its 82.55 mm shaft) into adjustment — the two references are separate engineering parts that happen to ship as one set. NTN grades inch 4T bearings as open bearings without integral seals; at 82.55 mm bore the application supplies sealing and the grease fill or oil feed.
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
- 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 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
- Mount the 82.55 mm cone by induction heating (max 120 °C) and the 150.089 mm cup with a press sleeve; at 3370 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 82.55 mm bore (150.089×44.45 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 749A/742 reference at purchase.
- Inch and metric bores collide on paper — 82.55 mm is 3.25 in, not a round metric size; a metric bearing that seems 0.1 mm off will not seat on the inch shaft.
- Never drive the 150.089 mm cup home through the rollers: fitting force goes through the ring faces only, or brinell marks release as noise within the first running hours.
- An unloaded 4T-749A/742 near 2,400 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded high-speed pairs.
- The 289/360 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-749A/742; 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-749A/742?
4T-749A/742 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 82.55 mm bore (3.25 in), 150.089 mm outside diameter and 44.45 mm assembled width T (5.909 × 1.75 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 289 kN, C0 360 kN, grease limiting speed 2,400 r/min, oil speed 3,200 r/min, mass about 3370 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-749A/742 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 749A cone or the 742 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 289/360 kN ratings change with the cup.
What is the difference between 4T-749A/742 and a metric ISO 355 tapered bearing?
4T-749A/742 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 82.55×150.089×44.45 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-749A/742 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 749A/742 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-749A/742 list two speeds, 2,400 and 3,200 r/min?
The lower figure, 2,400 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-749A/742 at 3,200 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.