29688-29620 bearing: complete specifications & equivalents
The 29688-29620 is a ANSI ABMA 19.2 radial bearing sized 73.817 x 112.712 x 25.4 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 73.817 mm |
| Outer diameter D | 112.712 mm |
| Width B | 25.4 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 106 kN |
| Basic static load rating C0 | 151 kN |
| Limiting speed (mechanical) | 3100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 862 g |
| Manufacturer designation | NTN 4T-29688/29620 |
| 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 | 2.906 in |
|---|---|
| Outer diameter D | 4.437 in |
| Width B | 1 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 19.4 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) | 91 of 148 |
| Bore above smallest 4t-inch-series size | 61.11699999999999 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 29688 | 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 29688-29620 model number is decoded
The NTN 2203E inch table prints 4T-29688/29620 at 73.817 mm bore (2.906 in), 112.712 mm cup OD and 25.4 mm assembled T, with a grease limiting speed of 3,100 r/min and an oil ceiling of 4,100 r/min. Cone and cup of 4T-29688/29620 are separately stocked parts: a worn 29620 cup can be replaced against the existing 29688 cone, provided the new cup carries the identical reference — pairing across references changes the 25.4 mm assembled width and the rating. Selection: C 106 kN against C0 151 kN gives a C0/C ratio of 1.42 for the 73.817 mm bore; the pair is counted as one adjusted unit when checking L10 at the equivalent combined load. Housing fitment sequence for 4T-29688/29620: press the 29620 cup square into the 112.712 mm seat first, then bring the 29688 cone (on its 73.817 mm shaft) into adjustment — the two references are separate engineering parts that happen to ship as one set. Running clearance of 4T-29688/29620 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
- marine winch and deck-machinery shafts
- crusher and screening-plant eccentric shafts
- heavy truck and bus drive-axle differentials
- plant gearboxes on inch-dimensioned shaft lines
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
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Mount the 73.817 mm cone by induction heating (max 120 °C) and the 112.712 mm cup with a press sleeve; at 862 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 73.817 mm bore (112.712×25.4 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 29688/29620 reference at purchase.
- Replacing one half of an adjusted pair without resetting end play negates the 25.4 mm T logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- Inch and metric bores collide on paper — 73.817 mm is 2.906 in, not a round metric size; a metric bearing that seems 0.1 mm off will not seat on the inch shaft.
- Fit selection follows the rotating ring: a rotating cone on a 73.817 mm shaft takes a k5/m5 seat, and a rotating cup reverses the logic — decide from the load diagram, not from habit.
- The 106/151 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-29688/29620; 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-29688/29620?
4T-29688/29620 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 73.817 mm bore (2.906 in), 112.712 mm outside diameter and 25.4 mm assembled width T (4.437 × 1 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 106 kN, C0 151 kN, grease limiting speed 3,100 r/min, oil speed 4,100 r/min, mass about 862 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-29688/29620 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 29688 cone or the 29620 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 106/151 kN ratings change with the cup.
What is the difference between 4T-29688/29620 and a metric ISO 355 tapered bearing?
4T-29688/29620 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 73.817×112.712×25.4 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-29688/29620 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 29688/29620 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-29688/29620 list two speeds, 3,100 and 4,100 r/min?
The lower figure, 3,100 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-29688/29620 at 4,100 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.