61904 bearing: complete specifications & equivalents
The 61904 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 | GCr15 |
| Seal / shield | open |
| 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 |
| Reference speed (thermal) | 43000 rpm |
| Limiting speed (mechanical) | 26000 rpm |
| Operating temperature | -40 to +150 °C |
| Mass | 37 g |
| Manufacturer designation | SKF 61904 |
| 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 | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 61904-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-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 (OPEN vs ZZ) — confirm sealing suits the duty. |
| 61904-2RS-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 61904-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-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 (OPEN 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 (OPEN vs ZZ) — confirm sealing suits the duty. |
| 61904-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×37×9 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 61904-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-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 (OPEN 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 (OPEN 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 model number is decoded
61904 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the thin 619xx section (diameter series 9 of ISO 15), multiplying bore code 04 by five gives the 20 mm bore; the 37 mm outside diameter and 9 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 20 mm shaft under normal load, catalogue practice seats it on a k5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. In the SKF catalogue this open execution carries the bare designation; protected variants are ordered separately as -2Z and -2RSH.
Typical equipment & failure modes
Common applications
- lay shafts and idler shafts
- textile machinery
- packaging machinery
- space-constrained gearboxes
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- cage damage from operation beyond the limiting speed
- electrical pitting in VFD-driven motors without grounding protection
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 61904; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
- 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.
- The open 61904 has no lubricant retention: grease escapes and contaminants migrate straight into the 20×37×9 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Storage matters for open bearings: 61904 leaves the factory with rust preventive only, so clean it and apply the service grease at assembly even if the rings look oily from the wrapper.
- Measure the shaft, do not trust the drawing: a 20 mm nominal journal worn by even 0.02 mm turns an interference seat into a creeping fit that frets the bore of 61904.
- Grease compatibility is not guaranteed between fills: mixing lithium and polyurea thickeners in a 61900-series position can soften the mixture and leak — clean out the old fill before switching grease types.
- The open 61904 needs external sealing and application-supplied lubrication; in the SKF catalogue the protected variants are separate order numbers 61904-2Z (shields) and 61904-2RSH (contact seals), not suffix-free 61904.
- 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 bearing?
A 61904 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 an open bearing with no seals or shields.
How should 61904 be mounted?
Apply the mounting force to the ring being fitted: on a 20 mm shaft seat the press load must pass through the inner-ring face only. A fitting sleeve and an arbor press are normally sufficient at this size. Never strike the outer ring, the cage or the seals.
What lubrication does 61904 need?
The open 61904 is lubricated by the application; a NLGI 2 lithium-soap grease filled to roughly 25–35% of the free volume is the common choice, with a defined relubrication interval.
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 is the SKF designation and catalogue data for 61904?
In the SKF Rolling Bearings catalogue this size is listed as 61904 — the open (unsealed) execution, 20×37×9 mm per ISO 15. Quoted values: C 6.37 kN, C0 3.65 kN, Pu 0.156 kN, limiting speed 26000 r/min, mass 37 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 61904.
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.