6309-M bearing: complete specifications & equivalents
The 6309-M 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 |
| Tolerance class | P0 |
| Cage | brass |
| 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) | 14000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 850 g |
| Manufacturer designation | 6309 M |
| 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 & 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-RSR | NSK | full Dimensions and internal design equivalent — standard interchange. | NSK counterpart NSK 6309VV on the same 45×100×25 mm envelope with ratings within 10 % — interchange after checking seal, cage and precision details on both pages. |
| 309 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope as SKF 309, but catalogue C/C0 differ (55.3/31.5 kN vs 55/44 kN) — envelope match only after a load check. |
| 309-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×25 mm envelope as SKF 309-2Z, but catalogue C/C0 differ (55.3/31.5 kN vs 55/44 kN) — envelope match only after a load check. |
| 6309 | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF SKF 6309 (open arrangement) shares the 45×100×25 mm envelope with ratings within 10 % — execution variant of the same size; boundary dimensions interchangeable. |
| 6309-ZZ | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF SKF 6309-2Z (two non-contact shields) shares the 45×100×25 mm envelope with ratings within 10 % — execution variant of the same size; boundary dimensions interchangeable. |
| 6309-2RS | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF SKF 6309-2RSH (two contact elastomer seals) shares the 45×100×25 mm envelope with ratings within 10 % — execution variant of the same size; boundary dimensions interchangeable. |
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-M model number is decoded
In the 6300-series, the last two digits encode the bore: 6309 carries code 09 = 45 mm (code × 5). The envelope is 45×100×25 mm (1.772×3.937×0.984 in) with a 27.5 mm radial section height, C 55.3 kN, C0 31.5 kN and Pu 1.34 kN. The open 6309 M carries no shields or seals and relies on application lubrication and external sealing. The M suffix identifies the machined brass cage execution, a separate order number from the pressed-steel version. Limiting speed 14000 r/min, catalogue mass 850 g.
Typical equipment & failure modes
Common applications
- industrial fans
- compressor drives
- machine tool auxiliaries
- agricultural gearboxes
Known failure patterns
- contamination wear when the open arrangement is used without external seals
- lubricant starvation where no regreasing interval is maintained
- raceway smearing under marginal lubrication at start-up
- electrical pitting in VFD-driven motors without shaft grounding
Selection pitfalls — read before you substitute
- The fatigue load limit is 1.34 kN; it feeds the equivalent-mean-load check, not the basic life calculation — do not substitute one for the other.
- Do not preload 6309-M to silence it: a deep-groove ball bearing is not angular-contact, and axial preload only raises temperature and shortens grease life.
- The M suffix on 6309-M denotes a machined brass cage: it is the choice for high speeds, marginal lubrication and shock/vibration duty, and it is temperature-tolerant where polymer cages are not — the 850 g quoted mass includes the heavier cage.
- Open 6309-M needs external sealing at the arrangement level; in dusty housings its life depends entirely on those external seals and the regreasing schedule.
- Plan a relubrication interval for 6309-M; run-to-failure on open deep-groove bearings is the dominant early-failure cause.
- Fillet radii must clear the 6309-M chamfer so the 25 mm-wide ring seats square; an oversized shaft radius creates point contact on the ring face.
Frequently asked questions
What are the dimensions of 6309-M?
The SKF 6309 M measures 45 mm bore × 100 mm OD × 25 mm width (1.772 × 3.937 × 0.984 in), mass about 850 g. It is open, with no shields or seals.
How does the bore code in 6309 work?
The final two digits of 6309 are bore code 09, multiplied by 5 to give 45 mm.
Which fits should I use for 6309-M?
With a rotating inner ring use roughly k5 on the shaft and H7 in the 100 mm housing; reverse the interference if the outer ring rotates.
How heavy is 6309-M?
Catalogue mass is 850 g for 6309 M; seal and cage executions of the same envelope differ by a few grams.
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.