61903-ZZ bearing: complete specifications & equivalents
The 61903-ZZ is a ISO 15 radial bearing sized 17 x 30 x 7 mm (bore x OD x width) with ZZ sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 17 mm |
| Outer diameter D | 30 mm |
| Width B | 7 mm |
| Material | GCr15 |
| Seal / shield | ZZ |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 4.62 kN |
| Basic static load rating C0 | 2.55 kN |
| Fatigue load limit Pu | 0.108 kN |
| Reference speed (thermal) | 50000 rpm |
| Limiting speed (mechanical) | 26000 rpm |
| Operating temperature | -30 to +120 °C |
| Mass | 17 g |
| Manufacturer designation | SKF 61903-2Z |
| 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 | 0.669 in |
|---|---|
| Outer diameter D | 1.181 in |
| Width B | 0.276 in |
| ISO bore code | 03 |
| Radial section height (D−d)/2 | 6.5 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) | 11 of 63 |
| Bore above smallest 61900-series size | 14 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61903-2RS-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 61903-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 61903-ZZ-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. |
| 61903 | 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 before substituting. |
| 61903-2RS-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 61903-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 61903-RSR-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant differs (ZZ vs RSR) — confirm sealing suits the duty. |
| 61903-ZZ-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. |
| 61903-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant (ZZ vs 2RS) and load ratings differ — confirm sealing and rating before substituting. |
| 61903-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant (ZZ vs OPEN) and load ratings differ — confirm sealing and rating before substituting. |
| 61903-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; seal variant (ZZ vs RSR) and load ratings differ — confirm sealing and rating before substituting. |
| 61903-ZZ-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 17×30×7 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| W61903-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 61903-2RS1 shares the 17×30×7 mm envelope but rates differently (4.62/2.55 kN vs 3.97/2.55 kN) — not a load-rating equivalent. |
| W61903-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 61903-2Z shares the 17×30×7 mm envelope but rates differently (4.62/2.55 kN vs 3.97/2.55 kN) — not a load-rating equivalent. |
| W61903 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 61903 shares the 17×30×7 mm envelope but rates differently (4.62/2.55 kN vs 3.97/2.55 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 61903-ZZ model number is decoded
61903-ZZ carries two non-contact sheet-steel shields that hold the factory grease in and keep coarse debris out; they do not seal against liquids. Within the thin 619xx section (diameter series 9 of ISO 15), its bore code 03 comes from the 10/12/15/17 mm exception table, giving a 17 mm bore; the 30 mm outside diameter and 7 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 17 mm shaft under normal load, catalogue practice seats it on a j5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. SKF's own suffix is 2Z (this page's industry-neutral spelling is -ZZ); catalogue number 61903-2Z.
Typical equipment & failure modes
Common applications
- clutch and transmission assemblies
- robotics and automation joints
- lay shafts and idler shafts
- textile machinery
Known failure patterns
- fine-particle abrasion when non-contact shields let dust past in dirty duty
- grease aging in the shield-for-life cavity with no relubrication path
- electrical pitting in VFD-driven motors without grounding protection
- raceway smearing under marginal lubrication at start-up
Selection pitfalls — read before you substitute
- Codes 00–03 are the exception series: 61903 takes its 17 mm bore from the 10/12/15/17 mm table, so two designations only a few millimetres apart can read alike on paper — order by measured shaft size, not by code arithmetic.
- The 619xx thin section (6.5 mm section height at 17 mm bore) trades load capacity for compactness; stiff, accurately aligned seats are essential or edge loading will spall the raceway early.
- ZZ shields are non-contact: 61903-ZZ blocks chips and coarse dust but is not waterproof — do not install it expecting a pressure-wash seal, step up to 61903-2RS for that.
- Shielded 61903-ZZ units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
- Never mix components between two 61903-ZZ units: rings, cage and balls are factory-matched and are not field-interchangeable, even between identical designations.
- Shaft and housing fillets must clear the bearing chamfer so the 7 mm-wide ring seats square; provide an undercut or withdrawal groove instead of relying on an oversized radius.
- SKF spells the shielded version 61903-2Z (one shield: 61903-Z), not "-ZZ": the suffix language differs by brand even though the ISO envelope is identical, so quote the brand designation when ordering.
- The 4.62/2.55 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 61903-ZZ bearing?
A 61903-ZZ deep-groove ball bearing has a 17 mm bore, 30 mm outer diameter and 7 mm width (0.669 × 1.181 × 0.276 in), per ISO 15 boundary dimensions. It is fitted with two non-contact metallic shields.
What internal clearance does 61903-ZZ have?
Unless a clearance suffix says otherwise, 61903-ZZ is manufactured to normal (CN) radial internal clearance. Tight fits and hot shafts consume clearance in service — for those conditions order the C3 execution of 61903 and verify the residual clearance after mounting.
How should 61903-ZZ be mounted?
Apply the mounting force to the ring being fitted: on a 17 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 61903-ZZ need?
61903-ZZ is greased at the factory and the shields hold the fill for the bearing's service life; relubrication is not intended, and adding grease through the shield gap usually forces dirt in with it.
What is the SKF designation and catalogue data for 61903-ZZ?
In the SKF Rolling Bearings catalogue this size is listed as 61903-2Z — two non-contact sheet-metal shields, 17×30×7 mm per ISO 15. Quoted values: C 4.62 kN, C0 2.55 kN, Pu 0.108 kN, limiting speed 26000 r/min, mass 17 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 61903-ZZ.
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.