NNU4980K bearing: complete specifications & equivalents
The NNU4980K is a ISO 15 radial bearing sized 400 x 540 x 140 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 400 mm |
| Outer diameter D | 540 mm |
| Width B | 140 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1870 kN |
| Basic static load rating C0 | 4300 kN |
| Fatigue load limit Pu | 325 kN |
| Limiting speed (mechanical) | 940 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 84100 g |
| Manufacturer designation | NTN NNU4980K |
| 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 | 15.748 in |
|---|---|
| Outer diameter D | 21.26 in |
| Width B | 5.512 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 70 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) | 22 of 26 |
| Bore above smallest NNU4900-series size | 300 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4980K | 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 NNU4980K model number is decoded
NTN lists NNU4980K on the 400×540 mm envelope, 140 mm wide: a line-contact radial bearing with a machined or stamped steel cage per the precision execution and a grease limiting speed of 940 r/min. Numbering ties NNU4980K to its envelope: type code NNU, series NNU4900, 400 mm bore; the 540×140 mm outline therefore swaps dimensionally with other ISO 15 bearings of the same code, though rib arrangements differ by prefix. At 1,100 r/min with oil versus 940 r/min with grease (a 160 r/min band), lubrication choice for NNU4980K is a thermal decision, not just a sealing one. Selection arithmetic: Pu 325 kN is the fatigue load limit feeding the adjusted-life equation, and the C0/C ratio of 2.30 (4300/1870 kN) shows the high-static-capacity proportioning of this 400 mm bore. Provide axial location with an adjacent locating bearing rather than expecting the float cylindrical set to hold thrust on the 400 mm shaft.
Typical equipment & failure modes
Common applications
- machine-tool main spindles requiring high radial stiffness
- precision gearbox and indexing-drive shafts
- high-rpm motorised grinding and milling spindles
- CNC lathe and machining-centre spindle radial sets
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
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- false brinelling on standby machines exposed to external vibration
- brinelling from static overload or impact during handling
Selection pitfalls — read before you substitute
- At 400 mm bore, oil-lubricated arrangements toward 1,100 r/min need positive flow and drain design; the 84100 g NNU4980K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NNU4980K skids at 940 r/min and fails by smearing long before L10 fatigue.
- Grease limiting speed 940 r/min and oil 1,100 r/min are different limits for NNU4980K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NNU4980K skids at 940 r/min and fails by smearing long before L10 fatigue.
- Grease limiting speed 940 r/min and oil 1,100 r/min are different limits for NNU4980K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- The 1870/4300 kN ratings, 325 kN Pu and 84100 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4980K (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 NNU4980K?
NNU4980K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 400 mm bore, 540 mm OD and 140 mm width (15.748 × 21.26 × 5.512 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1870 kN, C0 4300 kN, Pu 325 kN, grease limiting speed 940 r/min, oil 1,100 r/min, mass about 84100 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. NNU4980K 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. NNU4980K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4980K?
The K suffix denotes a 1:12 tapered bore. NNU4980K 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 NNU4980 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4980K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 445 mm. The nominal bore/OD remain 400/540 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 940 r/min grease / 1,100 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.