28985-28921 bearing: complete specifications & equivalents
The 28985-28921 is a ANSI ABMA 19.2 radial bearing sized 60.325 x 100 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 | 60.325 mm |
| Outer diameter D | 100 mm |
| Width B | 25.4 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 100 kN |
| Basic static load rating C0 | 134 kN |
| Limiting speed (mechanical) | 3500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 769 g |
| Manufacturer designation | NTN 4T-28985/28921 |
| 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 | 2.375 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 1 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 19.8 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) | 77 of 148 |
| Bore above smallest 4t-inch-series size | 47.625 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 28985 | 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 28985-28921 model number is decoded
For an inch shaft of 60.325 mm carrying combined radial and thrust load, NTN lists 4T-28985/28921, a single-row 4T tapered roller set of 100 kN C and 134 kN C0 inside the 100 mm OD cup. Cone and cup of 4T-28985/28921 are separately stocked parts: a worn 28921 cup can be replaced against the existing 28985 cone, provided the new cup carries the identical reference — pairing across references changes the 25.4 mm assembled width and the rating. The 19.8 mm radial section over the 60.325 mm bore positions the contact line of the pair; abutment shoulders and spacers are dimensioned from that geometry, not from the bore alone. Housing fitment sequence for 4T-28985/28921: press the 28921 cup square into the 100 mm seat first, then bring the 28985 cone (on its 60.325 mm shaft) into adjustment — the two references are separate engineering parts that happen to ship as one set. After bedding-in, re-check the end play of the adjusted 4T-28985/28921 pair — initial seating of the ring faces relaxes the setting slightly.
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
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- 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 fatigue when the pair runs continuously near the grease limiting speed without oil cooling
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Mount the 60.325 mm cone by induction heating (max 120 °C) and the 100 mm cup with a press sleeve; at 769 g a cocked ring brinells the raceway directly.
- The pure-numeric inch family at 60.325 mm bore (100×25.4 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 28985/28921 reference at purchase.
- Fit selection follows the rotating ring: a rotating cone on a 60.325 mm shaft takes a k5/m5 seat, and a rotating cup reverses the logic — decide from the load diagram, not from habit.
- Fit selection follows the rotating ring: a rotating cone on a 60.325 mm shaft takes a k5/m5 seat, and a rotating cup reverses the logic — decide from the load diagram, not from habit.
- Quote the full 28985/28921 pair at ordering: the 28985 cone also ships against sibling cups, and a cup from another reference changes the 25.4 mm assembled width and the rating.
- The 100/134 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-28985/28921; 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-28985/28921?
4T-28985/28921 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 60.325 mm bore (2.375 in), 100 mm outside diameter and 25.4 mm assembled width T (3.937 × 1 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 100 kN, C0 134 kN, grease limiting speed 3,500 r/min, oil speed 4,700 r/min, mass about 769 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-28985/28921 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 28985 cone or the 28921 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 100/134 kN ratings change with the cup.
What is the difference between 4T-28985/28921 and a metric ISO 355 tapered bearing?
4T-28985/28921 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 60.325×100×25.4 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-28985/28921 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 28985/28921 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-28985/28921 list two speeds, 3,500 and 4,700 r/min?
The lower figure, 3,500 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-28985/28921 at 4,700 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.