4304-ATN9 bearing: complete specifications & equivalents
The 4304-ATN9 is a ISO 15 radial bearing sized 20 x 52 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 | 20 mm |
| Outer diameter D | 52 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 | 23.4 kN |
| Basic static load rating C0 | 16 kN |
| Fatigue load limit Pu | 0.68 kN |
| Reference speed (thermal) | 22000 rpm |
| Limiting speed (mechanical) | 12000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 210 g |
| Manufacturer designation | 4304 ATN9 |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); 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 & 4300-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.827 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 16 mm |
| Smallest bore in 4300-series | 12 mm |
| Largest outer diameter in 4300-series | 160 mm |
| Width range across 4300-series | 17–55 mm |
| Bore position in 4300-series (smallest first) | 4 of 14 |
| Bore above smallest 4300-series size | 8 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 62304-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×52×21 mm envelope as SKF 62304-2RS1, but catalogue C/C0 differ (23.4/16 kN vs 15.9/7.8 kN) — envelope match only after a load check. |
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 4304-ATN9 model number is decoded
4304 ATN9 is a double-row deep-groove ball bearing in the 4300-series: the last two digits encode the bore: 4304 carries code 04 = 20 mm (code × 5). Two complete ball sets share the 20×52×21 mm (0.787×2.047×0.827 in) envelope, giving C 23.4 kN, C0 16 kN and Pu 0.68 kN, with reversing axial capacity a single-row bearing cannot match. ATN9 is the glass-fibre PA66 cage. Limiting speed 12000 r/min, mass 210 g. The arrangement is open and requires external sealing.
Typical equipment & failure modes
Common applications
- fans with axial thrust reversals
- industrial wheel arrangements
- double-supported pump impeller shafts
- gearbox layshafts with reversing axial load
Known failure patterns
- uneven load sharing between the two raceways when one ring is tilted
- polyamide cage embrittlement after sustained high-temperature service
- brinelling from static overload or hammer blows during mounting
- false brinelling from vibration while the shaft stands idle
Selection pitfalls — read before you substitute
- Fit both rings square on the shoulders: the narrow internal land between the two raceways of 4304-ATN9 is sensitive to cocking during pressing.
- The ATN9 cage is glass-fibre-reinforced polyamide 66: it is light and quiet but caps continuous service around 100–120 °C in oil/grease — above that use the pressed-steel or machined-cage version of the 20 mm position.
- Two deep-groove raceways in 4304-ATN9 share the load but need parallel seats; tilting the 21 mm-wide assembly loads one row heavily and can spall it early.
- The wide 20×52×21 mm envelope is not interchangeable with a single-row 6204 — the housing and shaft shoulders differ, so design the seat for the double-row width from the start.
- The ATN9 cage is glass-fibre-reinforced polyamide 66: it is light and quiet but caps continuous service around 100–120 °C in oil/grease — above that use the pressed-steel or machined-cage version of the 20 mm position.
- Mount by heating the inner ring (max 120 °C) — driving 4304-ATN9 home through the outer ring or balls brinells the raceways.
Frequently asked questions
What are the dimensions of 4304-ATN9?
Double-row 4304 ATN9 measures 20×52×21 mm (0.787×2.047×0.827 in), about 210 g.
What does ATN9 mean on 4304 ATN9?
A = double-row deep-groove arrangement, TN9 is a glass-fibre-reinforced polyamide 66 cage; it limits continuous temperature to roughly 100–120 °C.
How is 4304-ATN9 lubricated and sealed?
The ATN9 execution is open and greased/oiled by the application; provide external lip seals and a regreasing path for dirty duty.
What load does 4304-ATN9 carry?
C 23.4 kN, C0 16 kN and Pu 0.68 kN per catalogue 17000; both rows share the load when the rings sit parallel.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-27. Read our editorial & correction policy.