3304-A bearing: complete specifications & equivalents
The 3304-A 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 | steel, stamped ribbon (J-type) |
| 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 A |
| 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-ATN9 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×52×22.2 mm envelope with catalogue ratings within 10 %; 3304 ATN9 is the glass-fibre PA66 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-A model number is decoded
3304 A 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. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage. 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. At the printed limiting speed of 13,000 r/min the mean pitch diameter dm ≈ 36.0 mm implies a dn value around 468k mm·r/min; the 15,000 r/min reference speed is the thermal-planning figure under catalogue load. Speed-ratio note for this exact unit: the reference speed is 15,000 r/min against a 13,000 r/min limiting speed, i.e. a reference-to-limit ratio of 1.15.
Typical equipment & failure modes
Common applications
- compact pump and compressor drives
- textile machinery roller drives
- small two-bearing-housing arrangements
Known failure patterns
- two-direction thrust overload concentrating load on one row and spalling its raceway
- loss of controlled axial clearance (CB) after thermal growth removes residual play
- stamped steel cage noise and pocket wear in marginal-lubrication starts, where a brass-cage execution would survive
- 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
- The D executions have a two-piece inner ring: mount both halves square to each other, never press on the outer ring, and keep the split faces clean during fitting.
- The double-row 3304 takes thrust in both directions by itself — that is the reason to choose it over two single-row bearings: one housing bore, one fit, built-in set geometry.
- The D executions have a two-piece inner ring: mount both halves square to each other, never press on the outer ring, and keep the split faces clean during fitting.
- 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 A as the double a steel 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-A?
3304 A 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 A suffix mean?
A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage.
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.