NNU4956K bearing: complete specifications & equivalents
The NNU4956K is a ISO 15 radial bearing sized 280 x 380 x 100 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 280 mm |
| Outer diameter D | 380 mm |
| Width B | 100 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1030 kN |
| Basic static load rating C0 | 2200 kN |
| Fatigue load limit Pu | 187 kN |
| Limiting speed (mechanical) | 1400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 30200 g |
| Manufacturer designation | NTN NNU4956K |
| 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 | 11.024 in |
|---|---|
| Outer diameter D | 14.961 in |
| Width B | 3.937 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 50 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) | 16 of 26 |
| Bore above smallest NNU4900-series size | 180 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4956K | 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 NNU4956K model number is decoded
The NTN order number NNU4956K denotes a 280×380×100 mm (11.024 × 14.961 × 3.937 in) cylindrical roller bearing in the NNU4900 family, a machined or stamped steel cage per the precision execution. The leading NNU defines the rib arrangement (double row, ribbed outer ring, separable inner); the dimension-series digits and the two-digit bore code resolve to 280 mm, with 380 mm OD and 100 mm width from the ISO 15 general plan. The 50.0 mm radial section ((380−280)/2) frames the roller complement; capacity per millimetre of bore is about 3.7 kN/mm before application factors. Rating life at 1030 kN C assumes clean oil and adequate film; the 187 kN Pu floor means contamination derating — not the C rating alone — governs adjusted life in dusty gearboxes. After mounting verify the outer ring slides axially by hand at ambient temperature; a stuck float ring in a NNU4956K non-locating position preloads the bearing when the shaft grows.
Typical equipment & failure modes
Common applications
- high-speed turbine and turbo-blower rotor supports
- coordinate-measuring and semiconductor-equipment drives
- machine-tool main spindles requiring high radial stiffness
- precision gearbox and indexing-drive shafts
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- pressed-steel cage pocket wear when rollers skid at light load or too-thin lubricant
- grease starvation and cage drag when relubrication intervals are extended past the grease life
- false brinelling on standby machines exposed to external vibration
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
Selection pitfalls — read before you substitute
- At 280 mm bore, oil-lubricated arrangements toward 1,700 r/min need positive flow and drain design; the 30200 g NNU4956K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The K tapered bore of NNU4956K is driven up to a measured clearance: skipping the drive-up procedure in favour of a normal press fit leaves the precision spindle set either preloaded hot or loose under load.
- The 50.0 mm section at 280 mm bore leaves a narrow oil path; with the standard cage the relubrication groove and oil-level design must keep grease from churning in the 100 mm-wide cavity.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NNU4956K skids at 1,400 r/min and fails by smearing long before L10 fatigue.
- The 50.0 mm section at 280 mm bore leaves a narrow oil path; with the standard cage the relubrication groove and oil-level design must keep grease from churning in the 100 mm-wide cavity.
- The 1030/2200 kN ratings, 187 kN Pu and 30200 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4956K (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 NNU4956K?
NNU4956K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 280 mm bore, 380 mm OD and 100 mm width (11.024 × 14.961 × 3.937 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1030 kN, C0 2200 kN, Pu 187 kN, grease limiting speed 1,400 r/min, oil 1,700 r/min, mass about 30200 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. NNU4956K 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. NNU4956K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4956K?
The K suffix denotes a 1:12 tapered bore. NNU4956K 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 NNU4956 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4956K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 312 mm. The nominal bore/OD remain 280/380 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,400 r/min grease / 1,700 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.