NNU4964K bearing: complete specifications & equivalents
The NNU4964K is a ISO 15 radial bearing sized 320 x 440 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 | 320 mm |
| Outer diameter D | 440 mm |
| Width B | 118 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1370 kN |
| Basic static load rating C0 | 2970 kN |
| Fatigue load limit Pu | 242 kN |
| Limiting speed (mechanical) | 1200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 49100 g |
| Manufacturer designation | NTN NNU4964K |
| 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 | 12.598 in |
|---|---|
| Outer diameter D | 17.323 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) | 18 of 26 |
| Bore above smallest NNU4900-series size | 220 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4964K | 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 NNU4964K model number is decoded
NNU4964K is the extra-light (10/49) section of the NTN NNU4900 dimension series for a 320 mm shaft — 1370 kN of basic dynamic capacity in a 49100 g, open bearing. 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 320 mm, with 440 mm OD and 118 mm width from the ISO 15 general plan. The separable ring comes off without removing the roller assembly from the other ring, which eases inspection and lets the non-locating arrangement accommodate thermal shaft growth. Thermal planning around the 1,200 r/min grease ceiling should include the cage type (a machined or stamped steel cage per the precision execution) and oil-flow option to 1,400 r/min for continuously high-duty 320 mm positions. On NNU arrangements confirm which ring is separable before heating: forcing the ribbed ring off over the roller complement damages the cage and rib faces.
Typical equipment & failure modes
Common applications
- precision gearbox and indexing-drive shafts
- high-rpm motorised grinding and milling spindles
- CNC lathe and machining-centre spindle radial sets
- precision rotary-table and dividing-head bearings
Known failure patterns
- inner-ring raceway spalling from overload in the line-contact Hertzian zone
- cage distortion after a mounting blow carried through the roller set
- grease starvation and cage drag when relubrication intervals are extended past the grease life
- hard-particle indentation of raceways in unfiltered oil or open arrangements
- electrical pitting on VFD-driven motor shafts without grounding protection
Selection pitfalls — read before you substitute
- At 320 mm bore, oil-lubricated arrangements toward 1,400 r/min need positive flow and drain design; the 49100 g NNU4964K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 440 mm race brinells and releases as vibration within hours.
- The NNU rib arrangement is not interchangeable with another prefix on the same 320 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 440×118 mm envelope matches.
- Do not replace NNU4964K with a deep-groove ball bearing on rating alone: line contact gives 1370 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 EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 1370/2970 kN pair here belongs to NNU4964K as printed, not to the bare size.
- The 1370/2970 kN ratings, 242 kN Pu and 49100 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4964K (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 NNU4964K?
NNU4964K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 320 mm bore, 440 mm OD and 118 mm width (12.598 × 17.323 × 4.646 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1370 kN, C0 2970 kN, Pu 242 kN, grease limiting speed 1,200 r/min, oil 1,400 r/min, mass about 49100 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. NNU4964K 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. NNU4964K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4964K?
The K suffix denotes a 1:12 tapered bore. NNU4964K 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 NNU4964 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4964K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 359 mm. The nominal bore/OD remain 320/440 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,200 r/min grease / 1,400 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.