NU2308 bearing: complete specifications & equivalents
The NU2308 is a ISO 15 radial bearing sized 40 x 90 x 33 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 33 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 129 kN |
| Basic static load rating C0 | 120 kN |
| Fatigue load limit Pu | 15.3 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 9500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 930 g |
| Manufacturer designation | NU 2308 ECP |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & NU2300-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 1.299 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in NU2300-series | 20 mm |
| Largest outer diameter in NU2300-series | 750 mm |
| Width range across NU2300-series | 21–224 mm |
| Bore position in NU2300-series (smallest first) | 5 of 35 |
| Bore above smallest NU2300-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU2308-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×33 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| NJ2308-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NJ 2308 ECP is a different execution with its own cage/flange configuration. |
| NUP2308-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NUP 2308 ECP is a different execution with its own cage/flange configuration. |
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 NU2308 model number is decoded
SKF NU2308 (NU 2308 ECP) is the wide cylindrical roller choice for a 40 mm shaft — one row of precisely profiled rollers on ground raceways inside the 90×33 mm ISO 15 envelope. On the SKF nameplate, NU2308 follows the ISO 15 convention: NU for the separable-inner-ring type, 23 for the wide, final digits 08 for the 40 mm bore. The SKF catalogue adds the ECP suffix for the standard glass-fibre reinforced polyamide cage; ECJ (pressed steel) and ECM (machined brass) are alternative executions with different speed and temperature ratings. Speed planning uses two different ceilings: 8,000 r/min thermal reference and 9,500 r/min mechanical limiting speed. Fit selection follows the rotating ring — interference on a rotating inner ring — and the outer ring is free to slide axially in the housing; a 40 mm shaft typically takes a k5 seat with an H7 housing bore.
Typical equipment & failure modes
Common applications
- pump and compressor drive shafts
- electric-motor shafts in pumps and fans
- machine-tool main spindles (radial set)
- paper-machine wet-section rolls
Known failure patterns
- inner-ring raceway spalling from overload or contamination in the line-contact hertz zone
- outer-ring raceway fatigue after extended service at loads above the catalogue L10 rating
- polymer cage cracking or softening after sustained running above 120 °C or with incompatible lubricant
- surface distress (micro-pitting) when the EHL film falls below the composite roughness at high specific load
- hard-particle indentation of the raceway in unfiltered oil systems
Selection pitfalls — read before you substitute
- On this 40 mm bore, thermal expansion of the shaft can preload the inner ring if the fit is too tight; calculate the residual interference at operating temperature and confirm the outer ring can still slide axially in the housing.
- The NU2300 series at 40 mm bore (90×33 mm) is the wide-section cylindrical roller with higher capacity but lower speed limit than the standard NU300 counterpart; do not substitute without re-checking shaft shoulder diameters and dn limit.
- Open NU2308 units need application-supplied sealing and a defined lubricant supply; the line-contact hertz stress is higher than point contact, so film thickness is the first failure mode when viscosity drops.
- Catalogue reference speed and limiting speed are different limits: the 8,000 r/min reference is a thermal criterion under load, while the 9,500 r/min limiting value is the mechanical ceiling — observe both.
- The 129/120 kN ratings are SKF catalogue 17000 values for the ECP polymer-cage execution; SKF can revise internal geometry without changing the order number, so keep the catalogue version (PUB BU/P1 17000/1 EN, 2018) with the specification and re-verify for critical drives.
- SKF lists several executions of NU2308 (ECP polymer cage, ECJ pressed steel, ECM machined brass); they are not interchangeable order numbers — quote the full NU 2308 ECP designation when purchasing and match the execution to the speed and temperature requirements.
Frequently asked questions
What are the dimensions and catalogue data of NU2308?
The NU 2308 ECP is a single-row cylindrical roller bearing with 40 mm bore, 90 mm outer diameter and 33 mm width (1.575 × 3.543 × 1.299 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 129 kN, C0 120 kN, fatigue load limit Pu 15.3 kN, reference speed 8,000 r/min, limiting speed 9,500 r/min, mass about 930 g. It is an open, separable bearing with a glass-fibre reinforced polyamide cage.
How does the NU2308 bore code work?
The last two digits of NU2308 are bore code 08, so 08 × 5 = 40 mm bore. The 90 mm OD and 33 mm width come from the ISO 15 dimension-series plan, shared with other cylindrical bearings of the same code.
What does the ECP suffix mean on NU2308?
ECP stands for a glass-fibre reinforced polyamide cage (PA66), the SKF standard for this size. Alternative executions include ECJ (pressed steel cage) and ECM (machined brass cage), which have different speed and temperature ratings and are separate order numbers.
Can NU2308 take axial load?
No — the NU design has no ribs on the outer ring and cannot support axial load in either direction. It is intended for pure radial load with axial location provided by adjacent components. If axial location is required, consider NJ (one-direction) or NUP (two-direction) variants, or pair the NU bearing with a thrust or angular-contact bearing.
How does NU2308 compare with a ball bearing of the same bore?
A cylindrical roller bearing has line contact and much higher radial capacity than a ball bearing of the same bore, but it cannot take axial load in the NU design and is sensitive to misalignment (≈ 3–4 minutes of arc). Speed limits are generally lower than deep-groove ball bearings. A ball bearing cannot be dropped into a pure radial cylindrical-roller position without re-checking life and deflection, and vice versa.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings on 2026-09-26. Read our editorial & correction policy.