NU307 bearing: complete specifications & equivalents
The NU307 is a ISO 15 radial bearing sized 35 x 80 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 35 mm |
| Outer diameter D | 80 mm |
| Width B | 21 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 75 kN |
| Basic static load rating C0 | 63 kN |
| Fatigue load limit Pu | 8.15 kN |
| Reference speed (thermal) | 9500 rpm |
| Limiting speed (mechanical) | 11000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 470 g |
| Manufacturer designation | NU 307 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 | 1.378 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 0.827 in |
| ISO bore code | 07 |
| Radial section height (D−d)/2 | 22.5 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) | 5 of 34 |
| Bore above smallest NU300-series size | 18 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6307 | 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. |
| 6307-2RS | 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. |
| 6307-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. |
| N307-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF N 307 ECP is a different execution with its own cage/flange configuration. |
| NJ307-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NJ 307 ECP is a different execution with its own cage/flange configuration. |
| NUP307-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NUP 307 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 NU307 model number is decoded
NU 307 ECP belongs to the SKF single-row cylindrical roller range — the 35 mm bore entry in the NU300 series, dimensioned 80 mm OD and 21 mm wide to the ISO 15 boundary plan. Digit by digit, NU307 reads as bearing type NU (single-row, inner ring separable), standard series 3, and bore reference 07 resolving to 35 mm; 80 mm OD and 21 mm width are the matching ISO 15 boundary values. 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: 9,500 r/min thermal reference and 11,000 r/min mechanical limiting speed. For a 35 mm shaft the usual inner-ring seat is k5 with an H7 housing when the inner ring rotates; the outer ring slides axially to accommodate thermal expansion of the shaft.
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
- false brinelling on standby machines exposed to external vibration
Selection pitfalls — read before you substitute
- On this 35 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 NU300 series at 35 mm bore (80×21 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.
- The NU307 shares its ISO 15 envelope with other cylindrical bearings of the same code but is not a drop-in replacement for a ball bearing: it has no axial load capacity in the NU design, and a deep-groove bearing cannot replace its radial-capacity duty.
- The NU307 shares its ISO 15 envelope with other cylindrical bearings of the same code but is not a drop-in replacement for a ball bearing: it has no axial load capacity in the NU design, and a deep-groove bearing cannot replace its radial-capacity duty.
- The 75/63 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 NU307 (ECP polymer cage, ECJ pressed steel, ECM machined brass); they are not interchangeable order numbers — quote the full NU 307 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 NU307?
The NU 307 ECP is a single-row cylindrical roller bearing with 35 mm bore, 80 mm outer diameter and 21 mm width (1.378 × 3.15 × 0.827 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 75 kN, C0 63 kN, fatigue load limit Pu 8.15 kN, reference speed 9,500 r/min, limiting speed 11,000 r/min, mass about 470 g. It is an open, separable bearing with a glass-fibre reinforced polyamide cage.
How does the NU307 bore code work?
The last two digits of NU307 are bore code 07, so 07 × 5 = 35 mm bore. The 80 mm OD and 21 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 NU307?
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 NU307 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 NU307 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.