309-ZZ bearing: complete specifications & equivalents
The 309-ZZ is a ISO 15 radial bearing sized 45 x 100 x 25 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 | 45 mm |
| Outer diameter D | 100 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | ZZ |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 55 kN |
| Basic static load rating C0 | 44 kN |
| Fatigue load limit Pu | 1.86 kN |
| Reference speed (thermal) | 13000 rpm |
| Limiting speed (mechanical) | 6000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 880 g |
| Manufacturer designation | 309-2Z |
| 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 | 1.772 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 0.984 in |
| ISO bore code | 09 |
| Radial section height (D−d)/2 | 27.5 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) | 5 of 14 |
| Bore above smallest 300-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6309-RSR | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | NSK bearing NSK 6309VV on the same 45×100×25 mm envelope, but catalogue C/C0 differ (55/44 kN vs 58.5/32 kN) — envelope interchange only after a load check. |
| 6309-M | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope as SKF 6309 M, but catalogue C/C0 differ (55/44 kN vs 55.3/31.5 kN) — envelope match only after a load check. |
| 309 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 45×100×25 mm envelope and equivalent catalogue ratings; 309 is the open arrangement execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| 6309 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6309 shares the 45×100×25 mm envelope but catalogue C/C0 differ (55/44 kN vs 55.3/31.5 kN) — envelope match, not a load-rating equivalent. |
| 6309-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6309-2Z shares the 45×100×25 mm envelope but catalogue C/C0 differ (55/44 kN vs 55.3/31.5 kN) — envelope match, not a load-rating equivalent. |
| 6309-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6309-2RSH shares the 45×100×25 mm envelope but catalogue C/C0 differ (55/44 kN vs 55.3/31.5 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 309-ZZ model number is decoded
309-2Z is a filling-slot (notched-ring) deep-groove bearing in the legacy 300-series: the last two digits encode the bore: 309 carries code 09 = 45 mm (code × 5). The rings carry loading slots that allow extra balls during assembly, which is what gives the 45×100×25 mm envelope its C 55 kN and C0 44 kN ratings (Pu 1.86 kN). SKF spells the double shield 309-2Z (suffix 2Z); the shields are non-contact, retain grease and block coarse debris but are not liquid-tight. Limiting speed 6000 r/min, mass 880 g. These bearings are built for high purely-radial loads at moderate speeds.
Typical equipment & failure modes
Common applications
- hoists and winch gear trains
- eccentric and vibratory conveyors
- legacy machinery repairs
- slew 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
- false brinelling from vibration while the shaft stands idle
- fretting corrosion on a creeping shaft or housing seat
Selection pitfalls — read before you substitute
- Filling slots let more balls be packed into the 45×100 mm envelope, which is why 309-ZZ reaches C 55 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 309-ZZ, never pass the full radial load across the slot zone during mounting or the ring lip can crack.
- 309 uses the legacy SKF 200/300 numbering (light/heavy filling-slot series), not the modern 6200/6300 spelling; quote 309-2Z exactly when ordering replacements.
- Filling-slot bearings take heavy purely-radial load at moderate speed but little thrust; the 55/44 kN ratings assume radial loading — use deep-groove 6xxx where axial load matters.
- Shields on 309-ZZ retain grease but do not seal against water; for wet farm duty add external lip seals rather than trusting the shield.
- Mount by heating the inner ring (max 120 °C) — driving 309-ZZ home through the outer ring or balls brinells the raceways.
Frequently asked questions
What are the dimensions of 309-ZZ?
Filling-slot bearing 309-2Z measures 45×100×25 mm (1.772×3.937×0.984 in), about 880 g.
What does the designation 309 mean?
It is the legacy 200/300 filling-slot numbering: series 300 and bore code 09 = 45 mm. Filling-slot bearings predate the 6xxx deep-groove spelling.
What is a filling-slot bearing?
The inner and outer rings each have a loading slot; when aligned, extra balls can be inserted, raising radial rating (C 55 kN for 309-ZZ). The slots also make the rings separable.
Can 309-ZZ take axial load?
Very little: the filling slots interrupt the raceway shoulders, so thrust towards the open slot side can unload or jam the balls. Use a standard deep-groove 6xxx bearing for combined loads.
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.