6311 bearing: complete specifications & equivalents
The 6311 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 |
|---|---|
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 29 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 | 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) | 8000 rpm |
| Operating temperature | -40 to +150 °C |
| Mass | 1350 g |
| Manufacturer designation | SKF 6311 |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-24 |
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 | 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 | 10 mm |
| Largest outer diameter in 6300-series | 400 mm |
| Width range across 6300-series | 11–78 mm |
| Bore position in 6300-series (smallest first) | 12 of 30 |
| Bore above smallest 6300-series size | 45 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6311 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
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 model number is decoded
In the 6300-series (ISO 15 diameter series 3) the last two digits encode the bore: 6311 carries bore code 11 = 55 mm. Outside diameter 120 mm and width 29 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 55 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
- conveyor drives
- material-handling equipment
- industrial fans
- industrial electric motors
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- electrical pitting in VFD-driven motors without grounding protection
- raceway smearing under marginal lubrication at start-up
Selection pitfalls — read before you substitute
- Temperature rise and interference fits consume internal clearance on this 55 mm bore: a CN bearing on a tight, hot shaft can lose all residual clearance — size 6311 with C3 for those conditions.
- The 63xx medium series gains rating at 55 mm bore through a 120 mm OD and 29 mm width; the heavier rolling elements also trade away some speed versus a 6211.
- The open 6311 has no lubricant retention: grease escapes and contaminants migrate straight into the 55×120×29 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Open bearings tolerate the highest speeds in the 6300-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 6311 units.
- 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.
- The open 6311 needs external sealing and application-supplied lubrication; in the SKF catalogue the protected variants are separate order numbers 6311-2Z (shields) and 6311-2RSH (contact seals), not suffix-free 6311.
- The 74.1/45 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 6311 bearing?
A 6311 deep-groove ball bearing has a 55 mm bore, 120 mm outer diameter and 29 mm width (2.165 × 4.724 × 1.142 in), per ISO 15 boundary dimensions. It is an open bearing with no seals or shields. Geometry-based estimated mass is about 1322 g for a steel-cage unit; catalogue masses vary slightly with seal and cage design.
How does the 6311 bore code work?
The last two digits of 6311 are bore code 11, giving 11 × 5 = 55 mm bore. The 120 mm outside diameter and 29 mm width follow the ISO 15 diameter series, not the bore code alone.
What does no suffix on 6311 mean?
A bare 6311 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 55 mm bore?
The '3' is the medium diameter series: 120×29 mm, 32.5 mm radial section at 55 mm bore, carrying more load than a 6211 but needing a larger housing bore and giving up some speed.
What is the SKF designation and catalogue data for 6311?
In the SKF Rolling Bearings catalogue this size is listed as 6311 — the open (unsealed) execution, 55×120×29 mm per ISO 15. Quoted values: C 74.1 kN, C0 45 kN, Pu 1.9 kN, limiting speed 8000 r/min, mass 1350 g. Brand suffixes (2Z, 2RSH) differ from the industry-neutral spelling 6311.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-24. Read our editorial & correction policy.