NN4956K bearing: complete specifications & equivalents
The NN4956K 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 | 28800 g |
| Manufacturer designation | NTN NN4956K |
| 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 & NN4900-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 NN4900-series | 100 mm |
| Largest outer diameter in NN4900-series | 440 mm |
| Width range across NN4900-series | 40–118 mm |
| Bore position in NN4900-series (smallest first) | 16 of 18 |
| Bore above smallest NN4900-series size | 180 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN4956K | 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 NN4956K model number is decoded
For pure radial duty on a 280 mm shaft NTN supplies NN4956K: two integral ribs on the outer ring and a ribless, separable inner ring; the open execution is rated 1,400 r/min on grease and 1,700 r/min on oil. Numbering ties NN4956K to its envelope: type code NN, series NN4900, 280 mm bore; the 380×100 mm outline therefore swaps dimensionally with other ISO 15 bearings of the same code, though rib arrangements differ by prefix. Double-row NN precision cylindrical roller bearing: ribbed inner ring with a separable outer ring, two roller rows for high radial stiffness on machine-tool spindles; the K suffix is a 1:12 tapered bore — mounted on a tapered seat or adapter sleeve and driven up to a precise radial clearance/preload; precision classes P5/P4/P2 and clearance are ordered separately. Thermal planning around the 1,400 r/min grease ceiling should include the cage type (a machined or stamped steel cage per the precision execution) and oil-flow option to 1,700 r/min for continuously high-duty 280 mm positions. Keep the open bearing wrapped until fitting: the line-contact raceways of the 280 mm bore indent under a single hard particle, and the steel cage provides no sealing of its own.
Typical equipment & failure modes
Common applications
- coordinate-measuring and semiconductor-equipment drives
- machine-tool main spindles requiring high radial stiffness
- precision gearbox and indexing-drive shafts
- high-rpm motorised grinding and milling spindles
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- cage wear accelerated when the EA high-capacity roller complement runs continuously above its thermal balance
- grease starvation and cage drag when relubrication intervals are extended past the grease life
- fretting corrosion on a loose rotating shaft seat
- fretting corrosion on a loose rotating shaft seat
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 28800 g NN4956K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Do not replace NN4956K with a deep-groove ball bearing on rating alone: line contact gives 1030 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
- Grease limiting speed 1,400 r/min and oil 1,700 r/min are different limits for NN4956K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- 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 100 mm width and abutment faces must be square to the axis; a tilted spacer concentrates load across the roller set and shows as uneven raceway polish on the 280 mm inner ring.
- The 1030/2200 kN ratings, 187 kN Pu and 28800 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4956K (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 NN4956K?
NN4956K is an NTN NN 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 28800 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. NN4956K is the NN 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. NN4956K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4956K?
The K suffix denotes a 1:12 tapered bore. NN4956K 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 NN4956 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NN4956K?
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.