JM612949-JM612910 bearing: complete specifications & equivalents
The JM612949-JM612910 is a ANSI ABMA 19.2 radial bearing sized 70 x 115 x 29 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 70 mm |
| Outer diameter D | 115 mm |
| Width B | 29 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 138 kN |
| Basic static load rating C0 | 171 kN |
| Limiting speed (mechanical) | 3100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1120 g |
| Manufacturer designation | NTN 4T-JM612949/JM612910 |
| 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 | 2.756 in |
|---|---|
| Outer diameter D | 4.528 in |
| Width B | 1.142 in |
| ISO bore code | 49 |
| Radial section height (D−d)/2 | 22.5 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) | 88 of 148 |
| Bore above smallest 4t-inch-series size | 57.3 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| JM612949 | 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 JM612949-JM612910 model number is decoded
4T-JM612949/JM612910 is the NTN 4T catalogue entry for a 70×115×29 mm inch tapered roller bearing — an ABMA-dimensioned cone/cup set, not an ISO 355 metric bearing, even though the table quotes metric equivalents. Reading the designation: 4T-JM612949/JM612910 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 JM metric-envelope family lettering ties the pair to its boundary plan. Selection: C 138 kN against C0 171 kN gives a C0/C ratio of 1.24 for the 70 mm bore; the pair is counted as one adjusted unit when checking L10 at the equivalent combined load. Cup-side note for JM612910: within the JM metric-envelope family tables the JM612949 cone is listed against several cup options, and it is the cup that fixes the 115 mm OD and the 29 mm assembled width — quote the full JM612949/JM612910 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-JM612949/JM612910, not only the raceway, or the pair smears on the first overloaded start.
Typical equipment & failure modes
Common applications
- plant gearboxes on inch-dimensioned shaft lines
- large conveyor head pulleys in bulk-handling plant
- paper-machine and calender roll supports
- off-highway and forestry machine axles
Known failure patterns
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- false brinelling on a stationary pair exposed to vibration during transport or standby
- preload loss and noise after one bearing of the adjusted pair is replaced without resetting end play
- 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
- Mount the 70 mm cone by induction heating (max 120 °C) and the 115 mm cup with a press sleeve; at 1120 g a cocked ring brinells the raceway directly.
- The J-prefixed JM612949 code belongs to a metric-envelope inch family: its 70 mm bore is a round metric figure, yet the part still follows ABMA cone/cup numbering — do not substitute an ISO 355 metric 302/322 bearing of the same bore without checking OD, T and contact angle.
- Do not confuse T (29 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 — 70 mm is 2.756 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 JM612949 and JM612910; use undercut shoulders so the rings seat on the face, not on a radius.
- The 138/171 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-JM612949/JM612910; 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-JM612949/JM612910?
4T-JM612949/JM612910 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 70 mm bore (2.756 in), 115 mm outside diameter and 29 mm assembled width T (4.528 × 1.142 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 138 kN, C0 171 kN, grease limiting speed 3,100 r/min, oil speed 4,100 r/min, mass about 1120 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-JM612949/JM612910 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the JM612949 cone or the JM612910 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 138/171 kN ratings change with the cup.
What is the difference between 4T-JM612949/JM612910 and a metric ISO 355 tapered bearing?
4T-JM612949/JM612910 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 70×115×29 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-JM612949/JM612910 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 JM612949/JM612910 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-JM612949/JM612910 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-JM612949/JM612910 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.