61904-2RS bearing: complete specifications & equivalents
The 61904-2RS is a ISO 15 radial bearing sized 20 x 37 x 9 mm (bore x OD x width) with 2RS sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 20 mm |
| Outer diameter D | 37 mm |
| Width B | 9 mm |
| Material | GCr15 |
| Seal / shield | 2RS |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 6.37 kN |
| Basic static load rating C0 | 3.65 kN |
| Fatigue load limit Pu | 0.156 kN |
| Limiting speed (mechanical) | 12000 rpm |
| Operating temperature | -30 to +110 °C |
| Mass | 38 g |
| Manufacturer designation | SKF 61904-2RS1 |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-25 |
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 & 61900-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.457 in |
| Width B | 0.354 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 8.5 mm |
| Smallest bore in 61900-series | 3 mm |
| Largest outer diameter in 61900-series | 1120 mm |
| Width range across 61900-series | 3–118 mm |
| Bore position in 61900-series (smallest first) | 12 of 63 |
| Bore above smallest 61900-series size | 17 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61904-2RS-FAG | FAG | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 61904-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs OPEN) — confirm sealing suits the duty. |
| 61904-ZZ-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs ZZ) — confirm sealing suits the duty. |
| 61904-2RS-NSK | NSK | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 61904-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs OPEN) — confirm sealing suits the duty. |
| 61904-RSR-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs RSR) — confirm sealing suits the duty. |
| 61904-ZZ | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs ZZ) — confirm sealing suits the duty. |
| 61904-2RS-NTN | NTN | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 61904-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs OPEN) — confirm sealing suits the duty. |
| 61904-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs RSR) — confirm sealing suits the duty. |
| 61904-ZZ-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (2RS vs ZZ) — confirm sealing suits the duty. |
| W61904-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 61904-2RS1 shares the 20×37×9 mm envelope but rates differently (6.37/3.65 kN vs 5.53/3.65 kN) — not a load-rating equivalent. |
| W61904 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 61904 shares the 20×37×9 mm envelope but rates differently (6.37/3.65 kN vs 5.53/3.65 kN) — not a load-rating equivalent. |
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 61904-2RS model number is decoded
In the 61900-series (diameter series 9 of ISO 15) the last two digits encode the bore: 61904 carries bore code 04 = 20 mm. Outside diameter 37 mm and width 9 mm come from the ISO 15 boundary-dimensions general plan. Suffix -2RS denotes two contact-type elastomer seals over a lifetime grease fill; the sealing lips add drag compared with open or shielded versions. 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. SKF's contact-seal catalogue number is 61904-2RS1 (older text: -2RS1), mapped here from the industry-neutral -2RS spelling.
Typical equipment & failure modes
Common applications
- textile machinery
- packaging machinery
- space-constrained gearboxes
- clutch and transmission assemblies
Known failure patterns
- seal-lip hardening and loss of pre-grease in sustained high-temperature service
- grease-life expiry in the sealed-for-life cavity (no relubrication path)
- 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
- A 20 mm shaft for 61904 should be finished to Ra ≤ 1.6 µm with square seating faces; at this bore a scored or oval journal shows up directly as running noise and early raceway damage.
- The 619xx thin section (8.5 mm section height at 20 mm bore) trades load capacity for compactness; stiff, accurately aligned seats are essential or edge loading will spall the raceway early.
- Heat is the enemy of the sealed 61904-2RS: sustained running near the lip temperature limit hardens the rubber, after which grease escapes and dirt tracks in — watch the housing temperature in hot drives.
- Never wash a sealed 61904-2RS in solvent or press it home via the outer ring; solvent destroys the grease thickener and mounting force through the seal deforms the lip.
- Suffixes stack in a defined order — clearance follows the seal code, e.g. 61904-C3. No clearance suffix means normal CN clearance.
- Axial location must clamp the ring face, not the seal area: a shoulder or circlip bearing on the seal side of the 9 mm-wide ring of 61904-2RS drags the lip and overheats it.
- SKF catalogues the contact-sealed version as 61904-2RS1 (older printings may read -2RS1); it is shipped pre-greased and its 12000 r/min limiting speed is set by seal-lip drag and grease life versus the open bearing's 43000 r/min thermal reference speed.
- The 6.37/3.65 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 61904-2RS bearing?
A 61904-2RS deep-groove ball bearing has a 20 mm bore, 37 mm outer diameter and 9 mm width (0.787 × 1.457 × 0.354 in), per ISO 15 boundary dimensions. It is fitted with two contact rubber seals and is normally pre-greased.
How does the 61904 bore code work?
The last two digits of 61904 are bore code 04, giving 04 × 5 = 20 mm bore. The 37 mm outside diameter and 9 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the 2RS suffix on 61904-2RS mean?
2RS means two contact elastomer seals, one each side, usually over a lifetime grease fill. Sealing against dust and moisture is better than ZZ shields, but the lip drag lowers the speed and temperature ceiling.
How does the 61900 compare with other series at the same 20 mm bore?
619 is a thin section one step above 618: 37×9 mm with an 8.5 mm radial section at 20 mm bore; a 6204 on the same bore is substantially larger and more heavily rated.
What is the SKF designation and catalogue data for 61904-2RS?
In the SKF Rolling Bearings catalogue this size is listed as 61904-2RS1 — two contact elastomer seals over a lifetime grease fill, 20×37×9 mm per ISO 15. Quoted values: C 6.37 kN, C0 3.65 kN, Pu 0.156 kN, limiting speed 12000 r/min, mass 38 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 61904-2RS.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-25. Read our editorial & correction policy.