6311-M bearing: complete specifications & equivalents
The 6311-M is a ISO 15 radial bearing sized 55 x 120 x 29 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 29 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 74.1 kN |
| Basic static load rating C0 | 45 kN |
| Fatigue load limit Pu | 1.9 kN |
| Reference speed (thermal) | 12000 rpm |
| Limiting speed (mechanical) | 11000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1650 g |
| Manufacturer designation | 6311 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 | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.142 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 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) | 18 of 40 |
| Bore above smallest 6300-series size | 53 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6311-RSR | NSK | full Dimensions and internal design equivalent — standard interchange. | NSK counterpart NSK 6311VV on the same 55×120×29 mm envelope with ratings within 10 % — interchange after checking seal, cage and precision details on both pages. |
| 311 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 55×120×29 mm envelope as SKF 311, but catalogue C/C0 differ (74.1/45 kN vs 79.2/67 kN) — envelope match only after a load check. |
| 311-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 55×120×29 mm envelope as SKF 311-2Z, but catalogue C/C0 differ (74.1/45 kN vs 79.2/67 kN) — envelope match only after a load check. |
| 6311 | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF SKF 6311 (open arrangement) shares the 55×120×29 mm envelope with ratings within 10 % — execution variant of the same size; boundary dimensions interchangeable. |
| 6311-ZZ | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF SKF 6311-2Z (two non-contact shields) shares the 55×120×29 mm envelope with ratings within 10 % — execution variant of the same size; boundary dimensions interchangeable. |
| 6311-2RS | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF SKF 6311-2RSH (two contact elastomer seals) shares the 55×120×29 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 6311-M model number is decoded
In the 6300-series, the last two digits encode the bore: 6311 carries code 11 = 55 mm (code × 5). The envelope is 55×120×29 mm (2.165×4.724×1.142 in) with a 32.5 mm radial section height, C 74.1 kN, C0 45 kN and Pu 1.9 kN. The open 6311 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 11000 r/min, catalogue mass 1650 g.
Typical equipment & failure modes
Common applications
- compressor drives
- machine tool auxiliaries
- agricultural gearboxes
- industrial electric motors
Known failure patterns
- contamination wear when the open arrangement is used without external seals
- lubricant starvation where no regreasing interval is maintained
- cage damage from running beyond the limiting speed
- raceway smearing under marginal lubrication at start-up
Selection pitfalls — read before you substitute
- Fillet radii must clear the 6311-M chamfer so the 29 mm-wide ring seats square; an oversized shaft radius creates point contact on the ring face.
- Do not preload 6311-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 6311-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 1650 g quoted mass includes the heavier cage.
- Open 6311-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 6311-M; run-to-failure on open deep-groove bearings is the dominant early-failure cause.
- Do not preload 6311-M to silence it: a deep-groove ball bearing is not angular-contact, and axial preload only raises temperature and shortens grease life.
Frequently asked questions
What are the dimensions of 6311-M?
The SKF 6311 M measures 55 mm bore × 120 mm OD × 29 mm width (2.165 × 4.724 × 1.142 in), mass about 1650 g. It is open, with no shields or seals.
How does the bore code in 6311 work?
The final two digits of 6311 are bore code 11, multiplied by 5 to give 55 mm.
What load can 6311-M take?
Catalogue values for 6311 M: dynamic C 74.1 kN, static C0 45 kN, fatigue limit Pu 1.9 kN. Use C in life calculation and C0 for static checks at 55 mm bore.
What is the speed rating of 6311-M?
SKF lists a 12000 r/min thermal reference speed and a 11000 r/min mechanical limiting speed for 6311 M; real limits also depend on lubrication and fits.
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.