NUP304-ECP bearing: complete specifications & equivalents
The NUP304-ECP is a ISO 15 radial bearing sized 20 x 52 x 15 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 20 mm |
| Outer diameter D | 52 mm |
| Width B | 15 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 35.5 kN |
| Basic static load rating C0 | 26 kN |
| Fatigue load limit Pu | 3.25 kN |
| Reference speed (thermal) | 15000 rpm |
| Limiting speed (mechanical) | 18000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 160 g |
| Manufacturer designation | SKF NUP 304 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 & NUP300-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.591 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 16 mm |
| Smallest bore in NUP300-series | 20 mm |
| Largest outer diameter in NUP300-series | 300 mm |
| Width range across NUP300-series | 15–62 mm |
| Bore position in NUP300-series (smallest first) | 1 of 21 |
| Bore above smallest NUP300-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| N304-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 envelope 20×52×15 mm and equivalent catalogue ratings; the N execution differs in flange/retaining-ring configuration — boundary-dimension interchangeable, but axial-locating behaviour is not identical. |
| NJ304-ECP | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 envelope 20×52×15 mm and equivalent catalogue ratings; the NJ execution differs in flange/retaining-ring configuration — boundary-dimension interchangeable, but axial-locating behaviour is not identical. |
| NU304 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 envelope 20×52×15 mm and equivalent catalogue ratings; the NU execution differs in flange/retaining-ring configuration — boundary-dimension interchangeable, but axial-locating behaviour is not identical. |
| NU304 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 envelope 20×52×15 mm and equivalent catalogue ratings; the NU execution differs in flange/retaining-ring configuration — boundary-dimension interchangeable, but axial-locating behaviour is not identical. |
| NU304 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same ISO 15 envelope 20×52×15 mm and equivalent catalogue ratings; the NU execution differs in flange/retaining-ring configuration — boundary-dimension interchangeable, but axial-locating behaviour is not identical. |
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 NUP304-ECP model number is decoded
SKF NUP 304 ECP is a single-row caged cylindrical roller bearing sized 20×52×15 mm — a dimension series 3 (medium-section ISO 15 envelope), listed in SKF catalogue PUB BU/P1 17000 ch. 6.1. Reading the NUP prefix: two integral flanges on the outer ring plus one integral flange and one loose flange ring on the inner ring. This makes the execution a locating bearing that positions the shaft axially in both directions while keeping the cylindrical-roller radial capacity. The ECP suffix marks the E-design execution with a glass-fibre reinforced polyamide (PA66) cage, limited to 120 °C continuous. The glass-fibre reinforced polyamide (PA66) window-type cage is reflected in the published speeds and temperature limits. Load-per-bore for the 20 mm seat is about 1.77 kN/mm, typical of dimension series 3 (medium-section ISO 15 envelope); use C0 26 kN for static checks such as crane hook blocks standing under load. Mounting: the loose inner-ring flange must be fitted on the correct side and retained by the shaft abutment; never omit it during reassembly or the bearing loses its two-direction locating function. A 20 mm seat normally takes a k5 interference with an H7 housing bore when the inner ring rotates.
Typical equipment & failure modes
Common applications
- small pump rotor shafts
- small industrial electric-motor shafts
- light gearbox layshafts
- motor-cycle and small-engine transmissions
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 softening above 120 °C
- polymer cage cracking or softening after sustained running above 120 °C or with incompatible lubricant
- roller-end scoring from inadequate oil flow in the roller-raceway contact
- edge-loading fatigue after shaft deflection beyond the 3–4 minute alignment limit
- electrical pitting on VFD-driven shafts without grounding protection
Selection pitfalls — read before you substitute
- Do not use a NUP bearing where a floating non-locating bearing is required — the loose inner flange makes it a locating bearing
- The dimension series 3 (medium-section ISO 15 envelope) envelope is shared with the N/NU/NJ/NUP executions of 304, but flange configuration and axial-locating behaviour differ — quote the full SKF NUP 304 ECP and do not substitute rib styles without checking the shaft locating scheme.
- Shaft and housing fillets must clear the bearing chamfers; an oversized radius tilts the 15 mm-wide ring and concentrates load.
- Shaft and housing fillets must clear the bearing chamfers; an oversized radius tilts the 15 mm-wide ring and concentrates load.
- The 35.5/26 kN ratings are SKF catalogue 17000 (2018) values for the ECP execution; re-verify against the current catalogue for critical drives and keep the catalogue version with the specification.
Frequently asked questions
What are the dimensions and catalogue data of NUP304-ECP?
SKF NUP 304 ECP is a single-row caged cylindrical roller bearing with 20 mm bore, 52 mm OD and 15 mm width per ISO 15. SKF lists C 35.5 kN, C0 26 kN, Pu 3.25 kN, reference speed 15,000 r/min and limiting speed 18,000 r/min, mass about 160 g.
What does the NUP designation and ECP suffix mean?
The ECP suffix marks the E-design execution with a glass-fibre reinforced polyamide (PA66) cage, limited to 120 °C continuous. Structurally this execution has two integral flanges on the outer ring plus one integral flange and one loose flange ring on the inner ring.
Can NUP304-ECP take axial load and locate the shaft?
Yes, in both directions: the integral inner flange plus the loose flange ring close both axial paths. Do not pair it with another locating bearing without thermal clearance.
How does NUP304-ECP compare with the other executions in the same envelope?
The N/NU/NJ/NUP executions share the ISO 15 envelope and load ratings but differ in flange arrangement and axial-locating behaviour; quote the exact order number.
What limits the service life of this bearing most often?
Line-contact fatigue above the L10 rating, cage wear at light loads and high temperatures, and edge loading from misalignment beyond about 3–4 minutes of arc are the typical failure drivers.
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.