344-332-NTN bearing: complete specifications & equivalents
The 344-332-NTN is a ANSI ABMA 19.2 radial bearing sized 40 x 80 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 40 mm |
| Outer diameter D | 80 mm |
| Width B | 21 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 75.5 kN |
| Basic static load rating C0 | 75 kN |
| Limiting speed (mechanical) | 4700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 479 g |
| Manufacturer designation | NTN 4T-344/332 |
| 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 | 1.575 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 0.827 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 20 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) | 44 of 148 |
| Bore above smallest 4t-inch-series size | 27.3 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 344-332 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×80×21 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 344-332AA | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×80×21 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 344-332-NTN model number is decoded
4T-344/332 is the NTN 4T catalogue entry for a 40×80×21 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 — 344 sits in the pure-numeric inch family. Selection: C 75.5 kN against C0 75 kN gives a C0/C ratio of 0.99 for the 40 mm bore; the pair is counted as one adjusted unit when checking L10 at the equivalent combined load. Cup-side note for 332: within the pure-numeric inch family tables the 344 cone is listed against several cup options, and it is the cup that fixes the 80 mm OD and the 21 mm assembled width — quote the full 344/332 pair, never the cone alone. The rollers run with their large ends against the cone's guide rib; lubricant must reach that rib face of 4T-344/332, not only the raceway, or the pair smears on the first overloaded start.
Typical equipment & failure modes
Common applications
- mining and quarry conveyor drive pulleys
- machine-tool headstocks on inch spindles
- pump and blower drive shafts with combined load
- truck and trailer axle hubs on inch-dimensioned axles
Known failure patterns
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- preload loss and noise after one bearing of the adjusted pair is replaced without resetting end play
- false brinelling on a stationary pair exposed to vibration during transport or standby
- 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 40 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-344/332.
- The pure-numeric inch family at 40 mm bore (80×21 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 344/332 reference at purchase.
- Do not confuse T (21 mm, the assembled cone-plus-cup width) with the cone width when drawing spacers; an abutment sized to T leaves the cup unseated.
- Inch and metric bores collide on paper — 40 mm is 1.575 in, not a round metric size; a metric bearing that seems 0.1 mm off will not seat on the inch shaft.
- Shaft and housing fillets must clear the ring chamfers of 344 and 332; use undercut shoulders so the rings seat on the face, not on a radius.
- The 75.5/75 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-344/332; 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-344/332?
4T-344/332 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 40 mm bore (1.575 in), 80 mm outside diameter and 21 mm assembled width T (3.15 × 0.827 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 75.5 kN, C0 75 kN, grease limiting speed 4,700 r/min, oil speed 6,300 r/min, mass about 479 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-344/332 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 344 cone or the 332 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 75.5/75 kN ratings change with the cup.
What is the difference between 4T-344/332 and a metric ISO 355 tapered bearing?
4T-344/332 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 40×80×21 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-344/332 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 344/332 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-344/332 list two speeds, 4,700 and 6,300 r/min?
The lower figure, 4,700 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-344/332 at 6,300 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.