3304-ATN9 bearing: complete specifications & equivalents
The 3304-ATN9 is a ISO 15 radial bearing sized 20 x 52 x 22.2 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 | 22.2 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 23.6 kN |
| Basic static load rating C0 | 14.6 kN |
| Fatigue load limit Pu | 0.62 kN |
| Reference speed (thermal) | 15000 rpm |
| Limiting speed (mechanical) | 13000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 220 g |
| Manufacturer designation | 3304 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 & 3300-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.874 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 16 mm |
| Smallest bore in 3300-series | 15 mm |
| Largest outer diameter in 3300-series | 240 mm |
| Width range across 3300-series | 19–92.1 mm |
| Bore position in 3300-series (smallest first) | 3 of 20 |
| Bore above smallest 3300-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3304-A | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×52×22.2 mm envelope with catalogue ratings within 10 %; 3304 A is the stamped steel cage, open arrangement execution of this size — boundary dimensions interchangeable, execution differs. |
| 3304-A-2Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×52×22.2 mm envelope with catalogue ratings within 10 %; 3304 A-2Z is the stamped steel cage, shields (-2Z) execution of this size — boundary dimensions interchangeable, execution differs. |
| 3304-A-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×52×22.2 mm envelope with catalogue ratings within 10 %; 3304 A-2RS1 is the stamped steel cage, contact NBR seals (-2RS1) execution of this size — boundary dimensions interchangeable, execution differs. |
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 3304-ATN9 model number is decoded
3304 ATN9 is SKF's 20 mm-bore double-row angular-contact ball bearing of the 3300 series — two ball rows back-to-back for two-direction axial location in one unit, 20×52×22.2 mm. A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. glass-fibre reinforced PA66 cage, ball-centred (suffix TN9), with a 120 °C continuous-temperature ceiling. Envelope 20×52×22.2 mm (0.787×2.047×0.874 in), 16.0 mm radial section height, C 23.6 kN, C0 14.6 kN, Pu 0.62 kN.reference speed 15,000 r/min (thermal) and limiting speed 13,000 r/min (mechanical), catalogue mass 220 g. Envelope economics: the 22.2 mm width over a 16.0 mm section yields 1.39 mm of ring width per section millimetre, and the bearing weighs 220 g for 23.6 kN of dynamic capacity — about 9 g per rated kN. Speed planning distinguishes the two published ceilings mechanically: the cage and balls tolerate 13,000 r/min while thermal balance under catalogue load sets the 15,000 r/min reference; at dm ≈ 36.0 mm the corresponding dn is approximately 468k mm·r/min. Bore-to-OD planning: OD 52 over bore 20 is a 2.60× step for this size, and the 22.2 mm width gives a bore/width ratio of 0.90; use these ratios when housing space around the 20 mm shaft is the first constraint.
Typical equipment & failure modes
Common applications
- compact pump and compressor drives
- textile machinery roller drives
- small two-bearing-housing arrangements
Known failure patterns
- false brinelling on the loaded row while the shaft stands idle under vibration
- snap-ring groove or two-piece-ring damage when the D execution is pressed home through the wrong ring
- TN9 cage embrittlement in a hot gearbox position beyond the 120 °C polymer ceiling
- hard-particle indentation of the asymmetric raceway in unfiltered oil
- mounting score marks when the bearing is cocked over a burr or keyway
Selection pitfalls — read before you substitute
- Interference goes on the rotating ring (about k5 at 20 mm bore); the wide 22.2 mm ring is sensitive to tilted seats, so check squareness before clamping.
- Controlled axial clearance is the heart of the design: the A execution is produced to the standard double-row axial clearance; check residual clearance after mounting and at operating temperature.
- Controlled axial clearance is the heart of the design: the A execution is produced to the standard double-row axial clearance; check residual clearance after mounting and at operating temperature.
- Interference goes on the rotating ring (about k5 at 20 mm bore); the wide 22.2 mm ring is sensitive to tilted seats, so check squareness before clamping.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3304 ATN9 as the double atn9 execution; the other order numbers of the 3304 size are different products and may carry different ratings — always quote the full designation when purchasing.
Frequently asked questions
What are the dimensions and catalogue data of 3304-ATN9?
3304 ATN9 measures 20 mm bore × 52 mm OD × 22.2 mm width (0.787 × 2.047 × 0.874 in), mass about 220 g. SKF 17000 ratings: C 23.6 kN, C0 14.6 kN, Pu 0.62 kN, reference speed 15,000 r/min (thermal) and limiting speed 13,000 r/min (mechanical).
What does the ATN9 suffix mean?
A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. glass-fibre reinforced PA66 cage, ball-centred (suffix TN9), with a 120 °C continuous-temperature ceiling.
Which fits should I use?
With a rotating inner ring use roughly k5 on the 20 mm shaft and H7 in the 52 mm housing; check the wide ring seats square because the 22.2 mm width is sensitive to tilt.
Why choose the double-row 3304 instead of two single-row bearings?
The double-row bearing locates the shaft in both axial directions in one unit, in one housing bore and with factory-controlled axial clearance — a more compact arrangement than a pair, with no field matching of ground faces. A single-row pair offers adjustable preload instead.
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.