NNU4960K bearing: complete specifications & equivalents
The NNU4960K is a ISO 15 radial bearing sized 300 x 420 x 118 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 300 mm |
| Outer diameter D | 420 mm |
| Width B | 118 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1330 kN |
| Basic static load rating C0 | 2800 kN |
| Fatigue load limit Pu | 231 kN |
| Limiting speed (mechanical) | 1300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 46400 g |
| Manufacturer designation | NTN NNU4960K |
| Standard | ISO 15 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); 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 & NNU4900-series range
| Bore d | 11.811 in |
|---|---|
| Outer diameter D | 16.535 in |
| Width B | 4.646 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 60 mm |
| Smallest bore in NNU4900-series | 100 mm |
| Largest outer diameter in NNU4900-series | 650 mm |
| Width range across NNU4900-series | 40–170 mm |
| Bore position in NNU4900-series (smallest first) | 17 of 26 |
| Bore above smallest NNU4900-series size | 200 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4960K | 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 NNU4960K model number is decoded
The NTN order number NNU4960K denotes a 300×420×118 mm (11.811 × 16.535 × 4.646 in) cylindrical roller bearing in the NNU4900 family, a machined or stamped steel cage per the precision execution. On the NTN nameplate NNU states which ring carries the ribs, which determines whether NNU4960K floats or locates; the numeric remainder is the ISO 15 series and 300 mm bore reference, not a fit or clearance instruction. Minimum radial load matters: an unloaded NNU4960K at high speed skids its rollers and smears the raceway; spring preload or the rotor weight typically covers the requirement in motors and pumps. Speed ratio check: limiting 1,300 r/min is .87 of the 1,500 r/min oil value for NNU4960K; grease-churn heating closes that gap as fill quantity rises. Housing and shaft fillets must clear the ring chamfers of NNU4960K; an oversized radius locks the ring on its face and tilts the 118 mm-wide seat.
Typical equipment & failure modes
Common applications
- precision rotary-table and dividing-head bearings
- high-speed turbine and turbo-blower rotor supports
- coordinate-measuring and semiconductor-equipment drives
- machine-tool main spindles requiring high radial stiffness
Known failure patterns
- inner-ring raceway spalling from overload in the line-contact Hertzian zone
- pressed-steel cage pocket wear when rollers skid at light load or too-thin lubricant
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- rolling-contact fatigue after the catalogue L10 life is exceeded
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
Selection pitfalls — read before you substitute
- At 300 mm bore, oil-lubricated arrangements toward 1,500 r/min need positive flow and drain design; the 46400 g NNU4960K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Open NNU4960K units need application-supplied sealing and a defined lubricant schedule; film thickness is the first failure mode for line contact when viscosity drops at the 300 mm contact.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NNU4960K skids at 1,300 r/min and fails by smearing long before L10 fatigue.
- Grease limiting speed 1,300 r/min and oil 1,500 r/min are different limits for NNU4960K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- Do not replace NNU4960K with a deep-groove ball bearing on rating alone: line contact gives 1330 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
- The 1330/2800 kN ratings, 231 kN Pu and 46400 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4960K (standard execution); other makes sharing the ISO 15 envelope revise internal geometry without changing the order number, so keep the 2203E reference with the specification for critical drives.
Frequently asked questions
What are the dimensions and catalogue data of NNU4960K?
NNU4960K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 300 mm bore, 420 mm OD and 118 mm width (11.811 × 16.535 × 4.646 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1330 kN, C0 2800 kN, Pu 231 kN, grease limiting speed 1,300 r/min, oil 1,500 r/min, mass about 46400 g. It is open, with a machined or stamped steel cage per the precision execution.
What is the difference between NU, NJ, NUP, N and NF cylindrical roller bearings?
NN and NNU are double-row precision designs rather than single-row rib variants: NN has a ribbed inner ring and separable outer ring, NNU the reverse; both give high radial stiffness for spindles and are commonly ordered with P5/P4 precision and a K 1:12 tapered bore for preload setting. NNU4960K is the NNU execution.
What do the EA, E and ＊ suffixes mean on NTN cylindrical roller bearings?
EA is NTN's high-capacity design with a pressed sheet-steel cage and optimised roller complement in the same ISO 15 envelope; E marks the high-capacity design at the larger bores; the ＊ symbol printed before the code in the NTN catalogue marks the ULTAGE new-generation specification and is not typed as part of the order number. NNU4960K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4960K?
The K suffix denotes a 1:12 tapered bore. NNU4960K mounts on a tapered shaft seat or adapter sleeve and is driven up to a measured residual clearance or preload — this is how precision spindle bearings achieve stiffness without locknut guesswork; the cylindrical-bore NNU4960 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4960K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 339 mm. The nominal bore/OD remain 300/420 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,300 r/min grease / 1,500 r/min oil.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.