HM88649-HM88610 bearing: complete specifications & equivalents
The HM88649-HM88610 is a ANSI ABMA 19.2 radial bearing sized 34.925 x 72.233 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 | 34.925 mm |
| Outer diameter D | 72.233 mm |
| Width B | 25.4 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 72 kN |
| Basic static load rating C0 | 84.5 kN |
| Limiting speed (mechanical) | 5400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 489 g |
| Manufacturer designation | NTN 4T-HM88649/HM88610 |
| 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 | 1.375 in |
|---|---|
| Outer diameter D | 2.844 in |
| Width B | 1 in |
| ISO bore code | 49 |
| Radial section height (D−d)/2 | 18.7 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) | 34 of 148 |
| Bore above smallest 4t-inch-series size | 22.224999999999998 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| HM88649-610 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 34.925×72.233×25.4 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 HM88649-HM88610 model number is decoded
4T-HM88649/HM88610 belongs to the NTN inch 4T tapered roller range (heavy-medium HM family); cone and cup are ordered by their own references and are individually interchangeable with like-numbered parts. Reading the designation: 4T-HM88649/HM88610 follows the ABMA inch convention — the number before the slash is the cone (inner ring with roller set and cage), the number after the slash is the cup (outer ring), and the heavy-medium HM family lettering ties the pair to its boundary plan. Grease relubrication at the 5,400 r/min limiting speed targets the cone-rib contact; sustaining 7,200 r/min needs an oil supply directed at the large roller ends. Cup-side note for HM88610: within the heavy-medium HM family tables the HM88649 cone is listed against several cup options, and it is the cup that fixes the 72.233 mm OD and the 25.4 mm assembled width — quote the full HM88649/HM88610 pair, never the cone alone. Fillet radii must clear the chamfers of the HM88649 cone and HM88610 cup; undercut shoulders seat the rings fully instead of bridging on a radius.
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
- 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
- cage fatigue when the pair runs continuously near the grease limiting speed without oil cooling
- 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 34.925 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-HM88649/HM88610.
- The heavy-medium HM family is proportioned for a high thrust share; swapping to a lighter LM or pure-numeric series at the same 34.925 mm bore cuts axial capacity even when the envelope fits — re-verify the load split before downgrading.
- Do not confuse T (25.4 mm, the assembled cone-plus-cup width) with the cone width when drawing spacers; an abutment sized to T leaves the cup unseated.
- Open 4T-HM88649/HM88610 sets have no seals: a hub or gearbox needs external sealing or the 5,400 r/min grease figure is meaningless once water reaches the cone rib.
- An unloaded 4T-HM88649/HM88610 near 5,400 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded high-speed pairs.
- The 72/84.5 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-HM88649/HM88610; 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-HM88649/HM88610?
4T-HM88649/HM88610 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 34.925 mm bore (1.375 in), 72.233 mm outside diameter and 25.4 mm assembled width T (2.844 × 1 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 72 kN, C0 84.5 kN, grease limiting speed 5,400 r/min, oil speed 7,200 r/min, mass about 489 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-HM88649/HM88610 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the HM88649 cone or the HM88610 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 72/84.5 kN ratings change with the cup.
What is the difference between 4T-HM88649/HM88610 and a metric ISO 355 tapered bearing?
4T-HM88649/HM88610 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 34.925×72.233×25.4 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-HM88649/HM88610 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 HM88649/HM88610 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-HM88649/HM88610 list two speeds, 5,400 and 7,200 r/min?
The lower figure, 5,400 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-HM88649/HM88610 at 7,200 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.