NNU4968K bearing: complete specifications & equivalents
The NNU4968K is a ISO 15 radial bearing sized 340 x 460 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 | 340 mm |
| Outer diameter D | 460 mm |
| Width B | 118 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1410 kN |
| Basic static load rating C0 | 3150 kN |
| Fatigue load limit Pu | 252 kN |
| Limiting speed (mechanical) | 1100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 51700 g |
| Manufacturer designation | NTN NNU4968K |
| 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 | 13.386 in |
|---|---|
| Outer diameter D | 18.11 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) | 19 of 26 |
| Bore above smallest NNU4900-series size | 240 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4968K | 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 NNU4968K model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NNU4968K appears as a 340 mm bore single-row cylindrical roller bearing (1410 kN C / 3150 kN C0) with a machined or stamped steel cage per the precision execution, listed to the ISO 15 boundary plan. Numbering ties NNU4968K to its envelope: type code NNU, series NNU4900, 340 mm bore; the 460×118 mm outline therefore swaps dimensionally with other ISO 15 bearings of the same code, though rib arrangements differ by prefix. NTN ships these bearings open with normal (CN) radial clearance and P0 tolerance as standard; precision classes and C3/C4 clearance are separate order suffixes, not part of NNU4968K. With the inner ring rotating, catalogue practice is a m6/n6 shaft seat and an H7/H6 housing; the outer ring must remain free to creep slightly axially in non-locating NNU arrangements. After mounting verify the outer ring slides axially by hand at ambient temperature; a stuck float ring in a NNU4968K 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
- inner-ring raceway spalling from overload in the line-contact Hertzian zone
- cage wear accelerated when the EA high-capacity roller complement runs continuously above its thermal balance
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- brinelling from static overload or impact during handling
- fretting corrosion on a loose rotating shaft seat
Selection pitfalls — read before you substitute
- At 340 mm bore, oil-lubricated arrangements toward 1,300 r/min need positive flow and drain design; the 51700 g NNU4968K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 1410/3150 kN pair here belongs to NNU4968K as printed, not to the bare size.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 460 mm race brinells and releases as vibration within hours.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NNU4968K skids at 1,100 r/min and fails by smearing long before L10 fatigue.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 460 mm race brinells and releases as vibration within hours.
- The 1410/3150 kN ratings, 252 kN Pu and 51700 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4968K (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 NNU4968K?
NNU4968K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 340 mm bore, 460 mm OD and 118 mm width (13.386 × 18.11 × 4.646 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1410 kN, C0 3150 kN, Pu 252 kN, grease limiting speed 1,100 r/min, oil 1,300 r/min, mass about 51700 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. NNU4968K 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. NNU4968K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4968K?
The K suffix denotes a 1:12 tapered bore. NNU4968K 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 NNU4968 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4968K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 379 mm. The nominal bore/OD remain 340/460 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,100 r/min grease / 1,300 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.