305-ZZ bearing: complete specifications & equivalents
The 305-ZZ is a ISO 15 radial bearing sized 25 x 62 x 17 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 | 25 mm |
| Outer diameter D | 62 mm |
| Width B | 17 mm |
| Material | GCr15 |
| Seal / shield | ZZ |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 22.9 kN |
| Basic static load rating C0 | 15.6 kN |
| Fatigue load limit Pu | 0.67 kN |
| Reference speed (thermal) | 20000 rpm |
| Limiting speed (mechanical) | 10400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 240 g |
| Manufacturer designation | 305-2Z |
| 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 & 300-series range
| Bore d | 0.984 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 0.669 in |
| ISO bore code | 05 |
| Radial section height (D−d)/2 | 18.5 mm |
| Smallest bore in 300-series | 25 mm |
| Largest outer diameter in 300-series | 190 mm |
| Width range across 300-series | 17–43 mm |
| Bore position in 300-series (smallest first) | 1 of 14 |
| Bore above smallest 300-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| W6305-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×62×17 mm envelope, but the stainless and chrome-steel executions carry different catalogue ratings (22.9/15.6 kN vs 17.8/11.2 kN) — envelope match, not a load-rating equivalent; choose by corrosion versus load duty. |
| W6305-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×62×17 mm envelope, but the stainless and chrome-steel executions carry different catalogue ratings (22.9/15.6 kN vs 17.8/11.2 kN) — envelope match, not a load-rating equivalent; choose by corrosion versus load duty. |
| W6305 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×62×17 mm envelope, but the stainless and chrome-steel executions carry different catalogue ratings (22.9/15.6 kN vs 17.8/11.2 kN) — envelope match, not a load-rating equivalent; choose by corrosion versus load duty. |
| 305 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 25×62×17 mm envelope and equivalent catalogue ratings; 305 is the open arrangement execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| 6305 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6305 shares the 25×62×17 mm envelope but catalogue C/C0 differ (22.9/15.6 kN vs 23.4/11.6 kN) — envelope match, not a load-rating equivalent. |
| 6305-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6305-2Z shares the 25×62×17 mm envelope but catalogue C/C0 differ (22.9/15.6 kN vs 23.4/11.6 kN) — envelope match, not a load-rating equivalent. |
| 6305-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6305-2RSH shares the 25×62×17 mm envelope but catalogue C/C0 differ (22.9/15.6 kN vs 23.4/11.6 kN) — envelope match, not a load-rating equivalent. |
| 6305-RSR | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6305-2RZ shares the 25×62×17 mm envelope but catalogue C/C0 differ (22.9/15.6 kN vs 23.4/11.6 kN) — envelope match, 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 305-ZZ model number is decoded
305-2Z is a filling-slot (notched-ring) deep-groove bearing in the legacy 300-series: the last two digits encode the bore: 305 carries code 05 = 25 mm (code × 5). The rings carry loading slots that allow extra balls during assembly, which is what gives the 25×62×17 mm envelope its C 22.9 kN and C0 15.6 kN ratings (Pu 0.67 kN). SKF spells the double shield 305-2Z (suffix 2Z); the shields are non-contact, retain grease and block coarse debris but are not liquid-tight. Limiting speed 10400 r/min, mass 240 g. These bearings are built for high purely-radial loads at moderate speeds.
Typical equipment & failure modes
Common applications
- material-handling winches
- slow heavy gearboxes
- farm machinery and harvesters
- construction equipment drives
Known failure patterns
- spalling of the filling-slot edge when balls are hammered through the slot under heavy thrust loading
- dirt entering through the open slot area when external sealing is neglected
- electrical pitting in VFD-driven motors without shaft grounding
- edge loading from shaft deflection or housing misalignment
Selection pitfalls — read before you substitute
- Filling slots let more balls be packed into the 25×62 mm envelope, which is why 305-ZZ reaches C 22.9 kN — but the slots also mean the two rings separate when the balls align with them, so handle it as a loose-clearance design.
- The slots sit at one angular position: on 305-ZZ, never pass the full radial load across the slot zone during mounting or the ring lip can crack.
- 305 uses the legacy SKF 200/300 numbering (light/heavy filling-slot series), not the modern 6200/6300 spelling; quote 305-2Z exactly when ordering replacements.
- Filling-slot bearings take heavy purely-radial load at moderate speed but little thrust; the 22.9/15.6 kN ratings assume radial loading — use deep-groove 6xxx where axial load matters.
- Filling slots let more balls be packed into the 25×62 mm envelope, which is why 305-ZZ reaches C 22.9 kN — but the slots also mean the two rings separate when the balls align with them, so handle it as a loose-clearance design.
- Catalogue ratings for 305-ZZ (C 22.9 kN, C0 15.6 kN) are SKF figures from PUB BU/P1 17000; geometry revisions can change ratings without changing the designation, so keep the catalogue edition with the specification.
Frequently asked questions
What are the dimensions of 305-ZZ?
Filling-slot bearing 305-2Z measures 25×62×17 mm (0.984×2.441×0.669 in), about 240 g.
What does the designation 305 mean?
It is the legacy 200/300 filling-slot numbering: series 300 and bore code 05 = 25 mm. Filling-slot bearings predate the 6xxx deep-groove spelling.
Why use an old 300-series bearing instead of a 62xx?
For slow, heavy, purely-radial duty the extra balls give more capacity in the same bore, and the separable rings simplify assembly in blind housings; at high speed modern designs run better.
What fails on 305-ZZ?
Slot-edge chipping under thrust or shock, dirt ingress in the open design and cage wear past the 10400 r/min limiting speed are the typical failure modes.
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.