NNU4996K bearing: complete specifications & equivalents
The NNU4996K is a ISO 15 radial bearing sized 480 x 650 x 170 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 480 mm |
| Outer diameter D | 650 mm |
| Width B | 170 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 2530 kN |
| Basic static load rating C0 | 5900 kN |
| Fatigue load limit Pu | 425 kN |
| Limiting speed (mechanical) | 770 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 149000 g |
| Manufacturer designation | NTN NNU4996K |
| 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 | 18.898 in |
|---|---|
| Outer diameter D | 25.591 in |
| Width B | 6.693 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 85 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) | 26 of 26 |
| Bore above smallest NNU4900-series size | 380 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4996K | 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 NNU4996K model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NNU4996K appears as a 480 mm bore single-row cylindrical roller bearing (2530 kN C / 5900 kN C0) with a machined or stamped steel cage per the precision execution, listed to the ISO 15 boundary plan. Reading the code: NNU for the double-row precision type, then the ISO 15 diameter/width series and the bore code — ×5 = 480 mm (00–03 use the 10/12/15/17 exception table). NTN prints the raceway diameters for this size — Fw 534 mm — the envelope inside the 480/650 mm bore/OD where the rollers actually run. Mass 149000 g for the 480×650×170 mm NNU4996K execution covers the pressed-steel cage and full roller complement; substitute on mass plus rating, not envelope alone. Mount the separable inner ring + roller assembly on the shaft first and slide the outer ring into the housing; never press the outer ring through the rollers of NNU4996K.
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
- 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
- electrical pitting on VFD-driven motor shafts without grounding protection
- false brinelling on standby machines exposed to external vibration
Selection pitfalls — read before you substitute
- At 480 mm bore, oil-lubricated arrangements toward 910 r/min need positive flow and drain design; the 149000 g NNU4996K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The NNU rib arrangement is not interchangeable with another prefix on the same 480 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 650×170 mm envelope matches.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NNU4996K skids at 770 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 650 mm race brinells and releases as vibration within hours.
- The NNU rib arrangement is not interchangeable with another prefix on the same 480 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 650×170 mm envelope matches.
- The 2530/5900 kN ratings, 425 kN Pu and 149000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4996K (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 NNU4996K?
NNU4996K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 480 mm bore, 650 mm OD and 170 mm width (18.898 × 25.591 × 6.693 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 2530 kN, C0 5900 kN, Pu 425 kN, grease limiting speed 770 r/min, oil 910 r/min, mass about 149000 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. NNU4996K 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. NNU4996K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4996K?
The K suffix denotes a 1:12 tapered bore. NNU4996K 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 NNU4996 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4996K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 534 mm. The nominal bore/OD remain 480/650 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 770 r/min grease / 910 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.