NNU4928K bearing: complete specifications & equivalents
The NNU4928K is a ISO 15 radial bearing sized 140 x 190 x 50 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 140 mm |
| Outer diameter D | 190 mm |
| Width B | 50 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 251 kN |
| Basic static load rating C0 | 470 kN |
| Fatigue load limit Pu | 49 kN |
| Limiting speed (mechanical) | 3000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3760 g |
| Manufacturer designation | NTN NNU4928K |
| 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 | 5.512 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.969 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 25 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) | 6 of 26 |
| Bore above smallest NNU4900-series size | 40 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4928K | 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 NNU4928K model number is decoded
The NTN order number NNU4928K denotes a 140×190×50 mm (5.512 × 7.48 × 1.969 in) cylindrical roller bearing in the NNU4900 family, a machined or stamped steel cage per the precision execution. Reading the code: NNU for the double-row precision type, then the ISO 15 diameter/width series and the bore code — ×5 = 140 mm (00–03 use the 10/12/15/17 exception table). 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. Selection arithmetic: Pu 49 kN is the fatigue load limit feeding the adjusted-life equation, and the C0/C ratio of 1.87 (470/251 kN) shows the high-static-capacity proportioning of this 140 mm bore. Housing and shaft fillets must clear the ring chamfers of NNU4928K; an oversized radius locks the ring on its face and tilts the 50 mm-wide seat.
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
- 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
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- rolling-contact fatigue after the catalogue L10 life is exceeded
- rolling-contact fatigue after the catalogue L10 life is exceeded
Selection pitfalls — read before you substitute
- At 140 mm bore, oil-lubricated arrangements toward 3,600 r/min need positive flow and drain design; the 3760 g NNU4928K 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 140 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 190×50 mm envelope matches.
- Grease limiting speed 3,000 r/min and oil 3,600 r/min are different limits for NNU4928K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 251/470 kN pair here belongs to NNU4928K as printed, not to the bare size.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 251/470 kN pair here belongs to NNU4928K as printed, not to the bare size.
- The 251/470 kN ratings, 49 kN Pu and 3760 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4928K (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 NNU4928K?
NNU4928K is an NTN NNU double-row precision cylindrical roller bearing to ISO 15: 140 mm bore, 190 mm OD and 50 mm width (5.512 × 7.48 × 1.969 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 251 kN, C0 470 kN, Pu 49 kN, grease limiting speed 3,000 r/min, oil 3,600 r/min, mass about 3760 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. NNU4928K 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. NNU4928K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4928K?
The K suffix denotes a 1:12 tapered bore. NNU4928K 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 NNU4928 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4928K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 156 mm. The nominal bore/OD remain 140/190 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 3,000 r/min grease / 3,600 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.