NN4940K bearing: complete specifications & equivalents
The NN4940K 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 | 13300 g |
| Manufacturer designation | NTN NN4940K |
| 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 & NN4900-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 NN4900-series | 100 mm |
| Largest outer diameter in NN4900-series | 440 mm |
| Width range across NN4900-series | 40–118 mm |
| Bore position in NN4900-series (smallest first) | 12 of 18 |
| Bore above smallest NN4900-series size | 100 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN4940K | 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 NN4940K model number is decoded
The NTN order number NN4940K denotes a 200×280×80 mm (7.874 × 11.024 × 3.15 in) cylindrical roller bearing in the NN4900 family, a machined or stamped steel cage per the precision execution. On the NTN nameplate NN states which ring carries the ribs, which determines whether NN4940K floats or locates; the numeric remainder is the ISO 15 series and 200 mm bore reference, not a fit or clearance instruction. NTN prints the raceway diameters for this size — Fw 225 mm — the envelope inside the 200/280 mm bore/OD where the rollers actually run. Rating life at 615 kN C assumes clean oil and adequate film; the 110 kN Pu floor means contamination derating — not the C rating alone — governs adjusted life in dusty gearboxes. Heat the inner ring to max 120 °C for the 200 mm interference fit and support the ring face square during fitting; cocking over a keyway brinells the raceway before first rotation.
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
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
- electrical pitting on VFD-driven motor shafts without grounding protection
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 13300 g NN4940K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The K tapered bore of NN4940K is driven up to a measured clearance: skipping the drive-up procedure in favour of a normal press fit leaves the precision spindle set either preloaded hot or loose under load.
- 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 NN4940K as printed, not to the bare size.
- Open NN4940K 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 NN rib arrangement is not interchangeable with another prefix on the same 200 mm seat: double row, ribbed inner ring, separable outer. Swapping NU for NJ changes axial location behaviour even though the 280×80 mm envelope matches.
- The 615/1180 kN ratings, 110 kN Pu and 13300 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4940K (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 NN4940K?
NN4940K is an NTN NN 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 13300 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. NN4940K is the NN 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. NN4940K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4940K?
The K suffix denotes a 1:12 tapered bore. NN4940K 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 NN4940 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NN4940K?
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.