6309 bearing: complete specifications & equivalents
The 6309 is a ISO 15 radial bearing sized 45 x 100 x 25 mm (bore x OD x width). 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 | open |
| 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) | 9500 rpm |
| Operating temperature | -40 to +150 °C |
| Mass | 840 g |
| Manufacturer designation | SKF 6309 |
| 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 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; standard interchange — confirm clearance class and precision with the supplier. |
| 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 (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6309-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-RSR | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (OPEN vs RSR) — confirm sealing suits the duty. |
| 6309-ZZ-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 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 (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6309-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. |
| 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 (OPEN vs RSR) — confirm sealing suits the duty. |
| 6309-ZZ-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 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. | — |
| 1726309-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 1726309-2RS1 is a standard-inner-ring insert on the same 45x100x25 mm ISO 15 envelope with ratings within 10 %, but its outer surface is sphered for a Y-housing whereas this page is the cylindrical-OD deep-groove bearing — not interchangeable mounts. |
| 1726309-B-2RS1-VP274 | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 1726309B-2RS1/VP274 is a standard-inner-ring insert on the same 45x100x25 mm ISO 15 envelope with ratings within 10 %, but its outer surface is sphered for a Y-housing whereas this page is the cylindrical-OD deep-groove bearing — not interchangeable mounts. |
| 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 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. With no seal suffix the bearing is open: no shields or seals are fitted and lubrication is supplied by the application. 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. 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
- small gearboxes
- conveyors and drives
- agricultural equipment
- fans and blowers
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- raceway smearing under marginal lubrication at start-up
- edge loading from shaft deflection or housing misalignment
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.
- 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.
- The open 6309 has no lubricant retention: grease escapes and contaminants migrate straight into the 45×100×25 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Storage matters for open bearings: 6309 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.
- Do not quieten a noisy bearing by preloading it: the 6300-series is a deep-groove design, not angular-contact; axial preload raises temperature and shortens grease life.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 100 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6309.
- The open 6309 needs external sealing and application-supplied lubrication; in the SKF catalogue the protected variants are separate order numbers 6309-2Z (shields) and 6309-2RSH (contact seals), not suffix-free 6309.
- 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 bearing?
A 6309 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 an open bearing with no seals or shields.
What does no suffix on 6309 mean?
A bare 6309 designation means open: no shields or seals, normal CN radial clearance and P0 normal tolerance unless further suffixes are ordered. The application must supply and retain the lubrication.
How does the 6300 compare with other series at the same 45 mm bore?
The '3' is the medium diameter series: 100×25 mm, 27.5 mm radial section at 45 mm bore, carrying more load than a 6209 but needing a larger housing bore and giving up some speed.
Are 6309 bearings from different brands interchangeable?
For boundary dimensions, yes: every brand's 6309 uses the same ISO 15 envelope (45×100×25 mm). Load ratings, limiting speeds, clearance, precision class and sealing design can differ, so verify those in the supplier catalogue when substituting.
What is the SKF designation and catalogue data for 6309?
In the SKF Rolling Bearings catalogue this size is listed as 6309 — the open (unsealed) execution, 45×100×25 mm per ISO 15. Quoted values: C 55.3 kN, C0 31.5 kN, Pu 1.34 kN, limiting speed 9500 r/min, mass 840 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6309.
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.