NU305 bearing: complete specifications & equivalents
The NU305 is a ISO 15 radial bearing sized 25 x 62 x 17 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 25 mm |
| Outer diameter D | 62 mm |
| Width B | 17 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 46.5 kN |
| Basic static load rating C0 | 36.5 kN |
| Fatigue load limit Pu | 4.55 kN |
| Reference speed (thermal) | 12000 rpm |
| Limiting speed (mechanical) | 15000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 230 g |
| Manufacturer designation | NU 305 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 | 0.984 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 0.669 in |
| ISO bore code | 05 |
| Radial section height (D−d)/2 | 18.5 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) | 3 of 34 |
| Bore above smallest NU300-series size | 8 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6305 | 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. |
| 6305-2RS | 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. |
| 6305-RSR | 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. |
| 6305-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. |
| N305-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF N 305 ECP is a different execution with its own cage/flange configuration. |
| NJ305-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NJ 305 ECP is a different execution with its own cage/flange configuration. |
| NUP305-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 boundary envelope and equivalent catalogue ratings; SKF NUP 305 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 NU305 model number is decoded
The NU 305 ECP is a 25×62×17 mm single-row cylindrical roller bearing — the standard entry in the NU300 series, with separable inner ring and roller assembly for easy mounting. The code breaks down as type prefix NU (inner ring separable, no outer-ring ribs), series 3 (the standard), and bore code 05 = 25 mm; dimensions 25×62×17 mm therefore match the ISO 15 envelope. 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. Catalogue mass 230 g for the 25×62×17 mm open execution covers the polymer cage and standard roller complement; steel or brass cage variants differ slightly in mass and carry their own order numbers. The outer ring has no ribs and cannot locate the shaft axially; pair NU305 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
- agricultural machinery power-take-off shafts
- automotive alternator and starter shafts
- small conveyor drum bearings
- small electric-motor armature 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
- 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
- edge loading from shaft deflection beyond the bearing alignment limit (≈ 3-4 minutes of arc for single-row CRB)
Selection pitfalls — read before you substitute
- At a 25 mm bore the thin roller and raceway are sensitive to misalignment; keep shaft deflection within the 3–4 minute alignment limit and check seat runout (target Ra ≤ 0.8 µm) — a tilted NU305 develops edge loading and early spalling.
- The NU300 series at 25 mm bore (62×17 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.
- Open NU305 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.
- Open NU305 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.
- The 46.5/36.5 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 NU305 (ECP polymer cage, ECJ pressed steel, ECM machined brass); they are not interchangeable order numbers — quote the full NU 305 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 NU305?
The NU 305 ECP is a single-row cylindrical roller bearing with 25 mm bore, 62 mm outer diameter and 17 mm width (0.984 × 2.441 × 0.669 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 46.5 kN, C0 36.5 kN, fatigue load limit Pu 4.55 kN, reference speed 12,000 r/min, limiting speed 15,000 r/min, mass about 230 g. It is an open, separable bearing with a glass-fibre reinforced polyamide cage.
How does the NU305 bore code work?
The last two digits of NU305 are bore code 05, so 05 × 5 = 25 mm bore. The 62 mm OD and 17 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 NU305?
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 NU305 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 NU305 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.