NU320 bearing: complete specifications & equivalents
The NU320 is a ISO 15 radial bearing sized 100 x 215 x 47 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 100 mm |
| Outer diameter D | 215 mm |
| Width B | 47 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 450 kN |
| Basic static load rating C0 | 440 kN |
| Fatigue load limit Pu | 51 kN |
| Reference speed (thermal) | 3200 rpm |
| Limiting speed (mechanical) | 3800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 7450 g |
| Manufacturer designation | NU 320 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 & NU300-series range
| Bore d | 3.937 in |
|---|---|
| Outer diameter D | 8.465 in |
| Width B | 1.85 in |
| ISO bore code | 20 |
| Radial section height (D−d)/2 | 57.5 mm |
| Smallest bore in NU300-series | 17 mm |
| Largest outer diameter in NU300-series | 620 mm |
| Width range across NU300-series | 14–109 mm |
| Bore position in NU300-series (smallest first) | 18 of 34 |
| Bore above smallest NU300-series size | 83 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU320-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 100×215×47 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 6320-2RS | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Identical envelope but a different bearing type — confirm load and speed suitability before substitution. |
| 6320-ZZ | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Identical envelope but a different bearing type — confirm load and speed suitability before substitution. |
| N320-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF N 320 ECP is a different execution with its own cage/flange configuration. |
| NJ320-ECJ | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NJ 320 ECJ is a different execution with its own cage/flange configuration. |
| NUP320-ECJ | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NUP 320 ECJ 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 NU320 model number is decoded
In SKF catalogue PUB BU/P1 17000, NU320 appears as NU 320 ECP: an open, single-row cylindrical roller bearing in the NU300 series, with glass-fibre reinforced polyamide cage and line-contact geometry for high radial capacity. On the SKF nameplate, NU320 follows the ISO 15 convention: NU for the separable-inner-ring type, 3 for the standard, final digits 20 for the 100 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. With C 450 kN and C0 440 kN, the NU320 radial-capacity check is straightforward: keep the equivalent load P below the rating at the required L10; axial load is not supported by the NU design. The outer ring has no ribs and cannot locate the shaft axially; pair NU320 with a locating bearing (e.g. deep-groove ball or angular contact) or use an NJ/NUP variant if one-direction location is required.
Typical equipment & failure modes
Common applications
- paper-machine dryer and calender rolls
- cement-kiln support-roller shafts
- wind-turbine gearbox intermediate shafts
- marine propulsion gearbox shafts
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
- cage pocket wear from roller skidding at insufficient radial load or during start-up before oil film build-up
- roller-end scoring from inadequate oil flow in the roller-raceway contact
- hard-particle indentation of the raceway in unfiltered oil systems
Selection pitfalls — read before you substitute
- Mount the 100 mm bore NU320 by induction heating of the inner ring (max 120 °C — the polymer cage sets the ceiling, not the steel); driving it home through the rollers brinells the raceway.
- The NU300 series at 100 mm bore (215×47 mm) is the standard-section cylindrical roller envelope; stepping to a wide-section 22/23 variant changes OD, width and heat generation — it is not a drop-in swap when the housing and speed are fixed.
- Catalogue reference speed and limiting speed are different limits: the 3,200 r/min reference is a thermal criterion under load, while the 3,800 r/min limiting value is the mechanical ceiling — observe both.
- The 7450 g mass and 47 mm width mean abutment faces must be square to the axis within the bearing's own P0 tolerance; a tilted spacer tilts the outer ring and concentrates load on one roller row of NU320.
- The 450/440 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 NU320 (ECP polymer cage, ECJ pressed steel, ECM machined brass); they are not interchangeable order numbers — quote the full NU 320 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 NU320?
The NU 320 ECP is a single-row cylindrical roller bearing with 100 mm bore, 215 mm outer diameter and 47 mm width (3.937 × 8.465 × 1.85 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 450 kN, C0 440 kN, fatigue load limit Pu 51 kN, reference speed 3,200 r/min, limiting speed 3,800 r/min, mass about 7450 g. It is an open, separable bearing with a glass-fibre reinforced polyamide cage.
How does the NU320 bore code work?
The last two digits of NU320 are bore code 20, so 20 × 5 = 100 mm bore. The 215 mm OD and 47 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 NU320?
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 NU320 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 NU320 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.