6304-RSR bearing: complete specifications & equivalents
The 6304-RSR is a ISO 15 radial bearing sized 20 x 52 x 15 mm (bore x OD x width) with RSR sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Bore diameter d | 20 mm |
| Outer diameter D | 52 mm |
| Width B | 15 mm |
| Material | GCr15 |
| Seal / shield | RSR |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 15.9 kN |
| Basic static load rating C0 | 7.8 kN |
| Fatigue load limit Pu | 0.335 kN |
| Reference speed (thermal) | 30000 rpm |
| Limiting speed (mechanical) | 15000 rpm |
| Operating temperature | -30 to +120 °C |
| Mass | 150 g |
| Manufacturer designation | SKF 6304-2RSL |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-24 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-24
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 & 6300-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 6300-series | 10 mm |
| Largest outer diameter in 6300-series | 400 mm |
| Width range across 6300-series | 11–78 mm |
| Bore position in 6300-series (smallest first) | 5 of 30 |
| Bore above smallest 6300-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6304 | ISO 15 | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | ISO 15 boundary-dimension envelope; seal suffix convention varies by brand (2RS / DDU / LLU / 2RSR) — verify seal design and temperature range. Brand-specific OEM equivalents pending multi-source data. |
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 6304-RSR model number is decoded
In the 6300-series (ISO 15 diameter series 3) the last two digits encode the bore: 6304 carries bore code 04 = 20 mm. Outside diameter 52 mm and width 15 mm come from the ISO 15 boundary-dimensions general plan. Suffix -RSR denotes two low-friction non-contact elastomer seals; they keep coarse debris out with minimal drag but are not liquid-tight. For normal-load mounting with a rotating inner ring on a 20 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude.
Typical equipment & failure modes
Common applications
- small gearboxes
- conveyors and drives
- agricultural equipment
- fans and blowers
Known failure patterns
- ingress of fine dust or moisture past the non-contact lip in dirty or wet duty (RSR is not liquid-tight)
- lip-lubricant starvation if the bearing runs dry for extended periods
- edge loading from shaft deflection or housing misalignment
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- At a 20 mm bore, a shaft-seat burr or an overtight setscrew can score the thin inner ring of 6304-RSR; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
- The 63xx medium series gains rating at 20 mm bore through a 52 mm OD and 15 mm width; the heavier rolling elements also trade away some speed versus a 6204.
- RSR low-friction seals on 6304-RSR run faster than contact-seal 6304-2RS but let fine dust and moisture past the non-contact lip; in dirty or wet duty specify 6304-2RS instead.
- The non-contact lip of 6304-RSR does not retain a lifetime grease fill the way a contact seal does; confirm the regreasing interval for the 20 mm bore position before relying on it as sealed-for-life.
- Shaft and housing fillets must clear the bearing chamfer so the 15 mm-wide ring seats square; provide an undercut or withdrawal groove instead of relying on an oversized radius.
- SKF catalogues the low-friction seal as 6304-2RSL (suffix -2RSL or -2RZ): a non-contact elastomer lip that runs near the open 15000 r/min limiting speed, closer to the open bearing's 30000 r/min reference than the contact-seal version. It keeps coarse debris out without the drag of a contact seal, but is not liquid-tight — use 2RSH for wet or fine-dust positions.
- The 15.9/7.8 kN ratings here are SKF Explorer-class figures from catalogue PUB BU/P1 17000/1 EN (Oct 2018); SKF can revise internal geometry and ratings without changing the designation, so treat the catalogue version and date as part of the specification and re-verify for critical drives.
Frequently asked questions
What are the dimensions of a 6304-RSR bearing?
A 6304-RSR deep-groove ball bearing has a 20 mm bore, 52 mm outer diameter and 15 mm width (0.787 × 2.047 × 0.591 in), per ISO 15 boundary dimensions. It is fitted with two low-friction non-contact rubber seals.
How does the 6304 bore code work?
The last two digits of 6304 are bore code 04, giving 04 × 5 = 20 mm bore. The 52 mm outside diameter and 15 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the RSR suffix on 6304-RSR mean?
RSR means two low-friction non-contact rubber seals. They keep coarse debris out with minimal drag (speed close to the open bearing) but are not liquid-tight; use -2RS contact seals for wet or fine-dust environments.
How does the 6300 compare with other series at the same 20 mm bore?
The '3' is the medium diameter series: 52×15 mm, 16.0 mm radial section at 20 mm bore, carrying more load than a 6204 but needing a larger housing bore and giving up some speed.
What is the SKF designation and catalogue data for 6304-RSR?
In the SKF Rolling Bearings catalogue this size is listed as 6304-2RSL — two low-friction non-contact elastomer seals, 20×52×15 mm per ISO 15. Quoted values: C 15.9 kN, C0 7.8 kN, Pu 0.335 kN, limiting speed 15000 r/min, mass 150 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6304-RSR.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-24. Read our editorial & correction policy.