643-632 bearing: complete specifications & equivalents
The 643-632 is a ANSI ABMA 19.2 radial bearing sized 69.85 x 136.525 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 | 69.85 mm |
| Outer diameter D | 136.525 mm |
| Width B | 41.275 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 215 kN |
| Basic static load rating C0 | 262 kN |
| Limiting speed (mechanical) | 2800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2630 g |
| Manufacturer designation | NTN 4T-643/632 |
| 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 | 2.75 in |
|---|---|
| Outer diameter D | 5.375 in |
| Width B | 1.625 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 33.3 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) | 86 of 148 |
| Bore above smallest 4t-inch-series size | 57.14999999999999 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 643 | 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 643-632 model number is decoded
4T-643/632 is an NTN inch-series single-row tapered roller bearing: a separable cone-and-cup pair on the ABMA inch boundary plan, 69.85×136.525×41.275 mm (assembled width T), for a shaft of about 69.85 mm (2.75 in). Unlike ISO 355 metric numbers, this ABMA code does not encode the bore arithmetically: 643 identifies the cone of 69.85 mm (2.75 in) bore by catalogue lookup, and 632 fixes the 136.525 mm OD. The 33.3 mm radial section over the 69.85 mm bore positions the contact line of the pair; abutment shoulders and spacers are dimensioned from that geometry, not from the bore alone. Cup-side note for 632: within the pure-numeric inch family tables the 643 cone is listed against several cup options, and it is the cup that fixes the 136.525 mm OD and the 41.275 mm assembled width — quote the full 643/632 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-643/632; reverse the fit logic when the cup rotates.
Typical equipment & failure modes
Common applications
- crusher and screening-plant eccentric shafts
- heavy truck and bus drive-axle differentials
- plant gearboxes on inch-dimensioned shaft lines
- large conveyor head pulleys in bulk-handling plant
Known failure patterns
- cone-rib and roller large-end smearing when the adjusted pair runs with preload but starved lubricant film
- 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
- cage damage from a mounting blow transmitted through the roller complement
- brinell marks on cone and cup raceways from impact during handling or hammer fitting
Selection pitfalls — read before you substitute
- Mount the 69.85 mm cone by induction heating (max 120 °C) and the 136.525 mm cup with a press sleeve; at 2630 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 69.85 mm bore (136.525×41.275 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 643/632 reference at purchase.
- ABMA makes the 69.85×136.525 mm envelope interchangeable, not the ratings: NTN prints 215/262 kN for this execution and another make of the same number can differ in roller complement.
- Never drive the 136.525 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.
- Grease packs must leave free volume inside the 41.275 mm-wide set; over-greasing a pair churning near the oil-band speed of 3,800 r/min raises temperature and destroys the setting.
- The 215/262 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-643/632; 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-643/632?
4T-643/632 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 69.85 mm bore (2.75 in), 136.525 mm outside diameter and 41.275 mm assembled width T (5.375 × 1.625 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 215 kN, C0 262 kN, grease limiting speed 2,800 r/min, oil speed 3,800 r/min, mass about 2630 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-643/632 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 643 cone or the 632 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 215/262 kN ratings change with the cup.
What is the difference between 4T-643/632 and a metric ISO 355 tapered bearing?
4T-643/632 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 69.85×136.525×41.275 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-643/632 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 643/632 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-643/632 list two speeds, 2,800 and 3,800 r/min?
The lower figure, 2,800 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-643/632 at 3,800 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.