W61904 bearing: complete specifications & equivalents
The W61904 is a ISO 15 radial bearing sized 20 x 37 x 9 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 | 37 mm |
| Width B | 9 mm |
| Material | SS440C |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 5.53 kN |
| Basic static load rating C0 | 3.65 kN |
| Fatigue load limit Pu | 0.156 kN |
| Reference speed (thermal) | 43000 rpm |
| Limiting speed (mechanical) | 26000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 32 g |
| Manufacturer designation | W 61904 |
| 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 & 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-ZZ | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | NSK NSK 6904ZZ shares the 20×37×9 mm envelope but carries different catalogue ratings (5.53/3.65 kN vs 7/3.7 kN) — the stainless execution is not a load-rating equivalent. |
| W61904-2RS | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×37×9 mm envelope and equivalent catalogue ratings; W 61904-2RS1 is the two contact elastomer seals execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| 61904 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 61904 shares the 20×37×9 mm envelope but carries different catalogue ratings (5.53/3.65 kN vs 6.37/3.65 kN) — the stainless execution is not a load-rating equivalent. |
| 61904-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 61904-2RS1 shares the 20×37×9 mm envelope but carries different catalogue ratings (5.53/3.65 kN vs 6.37/3.65 kN) — the stainless execution is not a load-rating equivalent. |
| 61904-RSR | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 61904-2RZ shares the 20×37×9 mm envelope but carries different catalogue ratings (5.53/3.65 kN vs 6.37/3.65 kN) — the stainless execution is 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 W61904 model number is decoded
The W prefix denotes SKF stainless steel deep-groove bearings (X108CrMo17 / AISI 440C class rings). In the 61900-series, the last two digits encode the bore: 61904 carries code 04 = 20 mm (code × 5). Envelope 20×37×9 mm (0.787×1.457×0.354 in), C 5.53 kN, C0 3.65 kN, Pu 0.156 kN; limiting speed 26000 r/min and mass 32 g. The open W 61904 carries no shields or seals and relies on application lubrication and external sealing. Stainless is chosen for corrosion and washdown duty, not for extra load — the same-envelope chrome-steel bearing rates higher.
Typical equipment & failure modes
Common applications
- small pumps handling corrosive media
- bicycle and outdoor equipment
- appliances exposed to moisture
- food and beverage conveyors
Known failure patterns
- surface staining and pitting when even the stainless steel is left unlubricated in salty or acidic duty
- seal and grease failure before the rings corrode in sustained washdown service
- contamination wear when the open arrangement is used without external seals
- lubricant starvation where no regreasing interval is maintained
Selection pitfalls — read before you substitute
- Stainless bearings carry lower load ratings than chrome steel of the same envelope: W61904 is quoted at C 5.53 kN versus the 9 mm-wide 52100 version — do not swap on dimensions alone.
- Food, pharmaceutical and washdown positions need food-grade grease (e.g. NSF H1 registered) inside W61904; standard fill is industrial grease unless specified otherwise.
- Corrosion resistance depends on clean, undamaged surfaces: never weld near W61904 or scratch the raceways during mounting, since the damaged spot starts corrosion.
- Temperatures above roughly 300 °C temper the stainless races; even standard greases fail far earlier — keep W61904 inside the quoted grease temperature range.
- At 20 mm bore, C3 clearance is the safe choice when interference fits plus temperature rise consume the CN clearance; a hot tight bearing with no residual clearance fails fast.
- Assign interference to the rotating ring: on a conventional shaft-mounted 20 mm position the inner ring rotates, so use a k5/m6 shaft seat with an H7 housing — reverse the logic if the outer ring rotates.
Frequently asked questions
What are the dimensions of the stainless W61904?
SKF W 61904 measures 20×37×9 mm (0.787×1.457×0.354 in), about 32 g, C 5.53 kN.
What does the W in W 61904 mean?
W is the SKF prefix for stainless steel deep-groove bearings (rings in X108CrMo17 / AISI 440C class); the rest of the designation follows the normal series and bore rules.
Can I replace a chrome-steel bearing with stainless W61904?
The envelope matches, but stainless rates lower (C 5.53 kN for W 61904); for corrosive environments that trade-off is intended, for high loads it shortens life.
Is the stainless bearing magnetic?
Yes. Bearing stainless steels are martensitic (hardened) and magnetic; non-magnetic austenitic grades cannot be hardened enough for raceways and balls.
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.