LM503349A-LM503310 bearing: complete specifications & equivalents
The LM503349A-LM503310 is a ANSI ABMA 19.2 radial bearing sized 45.987 x 74.976 x 18 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 45.987 mm |
| Outer diameter D | 74.976 mm |
| Width B | 18 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 56.5 kN |
| Basic static load rating C0 | 71 kN |
| Limiting speed (mechanical) | 4700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 298 g |
| Manufacturer designation | NTN 4T-LM503349A/LM503310 |
| 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 | 1.811 in |
|---|---|
| Outer diameter D | 2.952 in |
| Width B | 0.709 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 14.5 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) | 57 of 148 |
| Bore above smallest 4t-inch-series size | 33.287000000000006 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| LM503349A-310 | SKF | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
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 LM503349A-LM503310 model number is decoded
4T-LM503349A/LM503310 is the NTN 4T catalogue entry for a 45.987×74.976×18 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-LM503349A/LM503310 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 light-medium LM family lettering ties the pair to its boundary plan. Imperial cross-check for the drawing: 45.987×74.976×18 mm converts to 1.811 × 2.952 × 0.709 in; the ABMA envelope swaps with like-numbered inch parts but the 56.5/71 kN ratings are NTN-specific. The printed 56.5/71 kN ratings belong to the assembled LM503349A+LM503310 pair; a sibling row using the same cone with a different cup carries its own rating row because the raceway track shifts with the cup. Running clearance of 4T-LM503349A/LM503310 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
- industrial gearboxes built to inch shafting
- construction-equipment pivot and wheel positions
- mining and quarry conveyor drive pulleys
- machine-tool headstocks on inch spindles
Known failure patterns
- cone-rib and roller large-end smearing when the adjusted pair runs with preload but starved lubricant film
- 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
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- water-induced pitting when the open bearing sees washdown without external seals
Selection pitfalls — read before you substitute
- Hub and pinion positions of this 45.987 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-LM503349A/LM503310.
- The light-medium LM family at 45.987 mm bore (74.976×18 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full LM503349A/LM503310 reference at purchase.
- Fit selection follows the rotating ring: a rotating cone on a 45.987 mm shaft takes a k5/m5 seat, and a rotating cup reverses the logic — decide from the load diagram, not from habit.
- Do not confuse T (18 mm, the assembled cone-plus-cup width) with the cone width when drawing spacers; an abutment sized to T leaves the cup unseated.
- Grease packs must leave free volume inside the 18 mm-wide set; over-greasing a pair churning near the oil-band speed of 6,300 r/min raises temperature and destroys the setting.
- The 56.5/71 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-LM503349A/LM503310; 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-LM503349A/LM503310?
4T-LM503349A/LM503310 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 45.987 mm bore (1.811 in), 74.976 mm outside diameter and 18 mm assembled width T (2.952 × 0.709 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 56.5 kN, C0 71 kN, grease limiting speed 4,700 r/min, oil speed 6,300 r/min, mass about 298 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-LM503349A/LM503310 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the LM503349A cone or the LM503310 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 56.5/71 kN ratings change with the cup.
What is the difference between 4T-LM503349A/LM503310 and a metric ISO 355 tapered bearing?
4T-LM503349A/LM503310 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 45.987×74.976×18 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-LM503349A/LM503310 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 LM503349A/LM503310 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-LM503349A/LM503310 list two speeds, 4,700 and 6,300 r/min?
The lower figure, 4,700 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-LM503349A/LM503310 at 6,300 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.