6309-ZZ bearing: complete specifications & equivalents
The 6309-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 / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 55.3 kN |
| Basic static load rating C0 | 31.5 kN |
| Fatigue load limit Pu | 1.34 kN |
| Reference speed (thermal) | 15000 rpm |
| Limiting speed (mechanical) | 7500 rpm |
| Operating temperature | -30 to +120 °C |
| Mass | 870 g |
| Manufacturer designation | SKF 6309-2Z |
| 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 & 6300-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 6300-series | 2 mm |
| Largest outer diameter in 6300-series | 500 mm |
| Width range across 6300-series | 3–95 mm |
| Bore position in 6300-series (smallest first) | 16 of 40 |
| Bore above smallest 6300-series size | 43 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6309 | 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. |
| 6309-2RS-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 6309-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 6309-RSR | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (ZZ vs RSR) — confirm sealing suits the duty. |
| 6309-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. |
| 6309-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 6309-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 6309-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (ZZ vs RSR) — confirm sealing suits the duty. |
| 6309-ZZ-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. |
| 7309 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| NU309 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| 6309-M | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 6309 M (machined brass cage, open arrangement) is the same-size execution on the 45×100×25 mm envelope with ratings within 10 % — boundary dimensions interchangeable. |
| 309 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 309 shares the 45×100×25 mm envelope but catalogue C/C0 differ — envelope match only after a load check. |
| 309-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 309-2Z shares the 45×100×25 mm envelope but catalogue C/C0 differ — envelope match only after a load check. |
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 6309-ZZ model number is decoded
In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6309 carries bore code 09 = 45 mm. Outside diameter 100 mm and width 25 mm come from the ISO 15 boundary-dimensions general plan. Suffix -ZZ denotes two non-contact metallic shields; they retain grease and block coarse debris but are not liquid-tight. For normal-load mounting with a rotating inner ring on a 45 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. SKF's own suffix is 2Z (this page's industry-neutral spelling is -ZZ); catalogue number 6309-2Z.
Typical equipment & failure modes
Common applications
- small gearboxes
- conveyors and drives
- agricultural equipment
- fans and blowers
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
- edge loading from shaft deflection or housing misalignment
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- Sizes around 45 mm bore are normally pressed on cold with a sleeve against the inner-ring face; the press force must never route through the outer ring or the balls of 6309-ZZ.
- The 63xx medium section at 45 mm bore gains dynamic rating through larger rolling elements on a 100 mm OD; the penalty is mass and a lower limiting speed than the 6209 — do not specify it for speed-critical shafts.
- ZZ shields are non-contact: 6309-ZZ blocks chips and coarse dust but is not waterproof — do not install it expecting a pressure-wash seal, step up to 6309-2RS for that.
- Do not wash 6309-ZZ in solvent before mounting: the grease inside the shielded cavity is the service fill, and solvent creeping past the shield gap strips it out.
- Assign fits by which ring rotates: an interference shaft fit for a rotating inner ring; if the outer ring rotates instead, reverse the logic — a loose rotating ring creeps and frets its seat.
- Never mix components between two 6309-ZZ units: rings, cage and balls are factory-matched and are not field-interchangeable, even between identical designations.
- SKF spells the shielded version 6309-2Z (one shield: 6309-Z), not "-ZZ": the suffix language differs by brand even though the ISO envelope is identical, so quote the brand designation when ordering.
- The single-shield execution 6309-Z is a distinct order number in catalogue 17000: it suits open gears or oil-bath arrangements where the unshielded face faces the lubricant, and it is not interchangeable with the double-shield 6309-2Z for high-contamination positions.
- The 55.3/31.5 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 6309-ZZ bearing?
A 6309-ZZ deep-groove ball bearing has a 45 mm bore, 100 mm outer diameter and 25 mm width (1.772 × 3.937 × 0.984 in), per ISO 15 boundary dimensions. It is fitted with two non-contact metallic shields.
What lubrication does 6309-ZZ need?
6309-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.
How does the 6309 bore code work?
The last two digits of 6309 are bore code 09, giving 09 × 5 = 45 mm bore. The 100 mm outside diameter and 25 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the ZZ suffix on 6309-ZZ mean?
ZZ means two non-contact sheet-metal shields, one each side. They retain factory grease and block coarse particles with little friction, but do not seal against liquids, fine dust or pressure washing.
What is the SKF designation and catalogue data for 6309-ZZ?
In the SKF Rolling Bearings catalogue this size is listed as 6309-2Z — two non-contact sheet-metal shields, 45×100×25 mm per ISO 15. Quoted values: C 55.3 kN, C0 31.5 kN, Pu 1.34 kN, limiting speed 7500 r/min, mass 870 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6309-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.