NNU4940K bearing: complete specifications & equivalents
The NNU4940K is a ISO 15 radial bearing sized 200 x 280 x 80 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 200 mm |
| Outer diameter D | 280 mm |
| Width B | 80 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 615 kN |
| Basic static load rating C0 | 1180 kN |
| Fatigue load limit Pu | 110 kN |
| Limiting speed (mechanical) | 2100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 14000 g |
| Manufacturer designation | NTN NNU4940K |
| 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 | 7.874 in |
|---|---|
| Outer diameter D | 11.024 in |
| Width B | 3.15 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 40 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) | 12 of 26 |
| Bore above smallest NNU4900-series size | 100 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4940K | 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 NNU4940K model number is decoded
NNU4940K belongs to the NTN cylindrical roller range in NTN Ball and Roller Bearings CAT.No.2203E: line-contact rollers between ground raceways for a 615 kN dynamic rating in the 200 mm bore. Reading the code: NNU for the double-row precision type, then the ISO 15 diameter/width series and the bore code — ×5 = 200 mm (00–03 use the 10/12/15/17 exception table). The 80 mm width and 40.0 mm section put the NNU4900 series in the extra-light (10/49) section; wide 22/23 variants at the same bore change OD, width and heat generation and are not drop-in swaps. The 200 mm (7.874 in) bore and 280 mm (11.024 in) OD are ISO 15 boundary values; fillet and shoulder dimensions must still come from the NTN mounting table for the 80 mm-wide ring. 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 NNU4940K.
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
- 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
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- hard-particle indentation of raceways in unfiltered oil or open arrangements
- false brinelling on standby machines exposed to external vibration
Selection pitfalls — read before you substitute
- At 200 mm bore, oil-lubricated arrangements toward 2,400 r/min need positive flow and drain design; the 14000 g NNU4940K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The 80 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 200 mm inner ring.
- Wide (22/23) and light (10/49) executions at 200 mm bore share bore but not OD/width; check the full NNU4900 series code before substituting, because housing and shoulder geometry will not interchange.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 615/1180 kN pair here belongs to NNU4940K as printed, not to the bare size.
- Open NNU4940K units need application-supplied sealing and a defined lubricant schedule; film thickness is the first failure mode for line contact when viscosity drops at the 200 mm contact.
- The 615/1180 kN ratings, 110 kN Pu and 14000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4940K (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 NNU4940K?
NNU4940K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 200 mm bore, 280 mm OD and 80 mm width (7.874 × 11.024 × 3.15 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 615 kN, C0 1180 kN, Pu 110 kN, grease limiting speed 2,100 r/min, oil 2,400 r/min, mass about 14000 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. NNU4940K 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. NNU4940K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4940K?
The K suffix denotes a 1:12 tapered bore. NNU4940K 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 NNU4940 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4940K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 225 mm. The nominal bore/OD remain 200/280 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 2,100 r/min grease / 2,400 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.