6318 bearing: complete specifications & equivalents
The 6318 is a ISO 15 radial bearing sized 90 x 190 x 43 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Bore diameter d | 90 mm |
| Outer diameter D | 190 mm |
| Width B | 43 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 | 151 kN |
| Basic static load rating C0 | 108 kN |
| Fatigue load limit Pu | 3.8 kN |
| Reference speed (thermal) | 7500 rpm |
| Limiting speed (mechanical) | 4800 rpm |
| Operating temperature | -40 to +150 °C |
| Mass | 4950 g |
| Manufacturer designation | SKF 6318 |
| 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 | 3.543 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.693 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 50 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) | 19 of 30 |
| Bore above smallest 6300-series size | 80 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6318 | 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 6318 model number is decoded
In the 6300-series (ISO 15 diameter series 3) the last two digits encode the bore: 6318 carries bore code 18 = 90 mm. Outside diameter 190 mm and width 43 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 90 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
- heavy conveyors
- pulp and paper machinery
- medium and heavy industrial drives
- large gearboxes
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- cage damage from operation beyond the limiting speed
- electrical pitting in VFD-driven motors without grounding protection
Selection pitfalls — read before you substitute
- Mount this 90 mm bore bearing by heating the inner ring (induction heater, max 120 °C) — never drive it home through the outer ring or balls, that brinells the raceways.
- The 63xx medium series gains rating at 90 mm bore through a 190 mm OD and 43 mm width; the heavier rolling elements also trade away some speed versus a 6218.
- The open 6318 has no lubricant retention: grease escapes and contaminants migrate straight into the 90×190×43 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 6318 units.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 190 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6318.
- The open 6318 needs external sealing and application-supplied lubrication; in the SKF catalogue the protected variants are separate order numbers 6318-2Z (shields) and 6318-2RSH (contact seals), not suffix-free 6318.
- The 151/108 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 6318 bearing?
A 6318 deep-groove ball bearing has a 90 mm bore, 190 mm outer diameter and 43 mm width (3.543 × 7.48 × 1.693 in), per ISO 15 boundary dimensions. It is an open bearing with no seals or shields. Geometry-based estimated mass is about 4825 g for a steel-cage unit; catalogue masses vary slightly with seal and cage design.
How does the 6318 bore code work?
The last two digits of 6318 are bore code 18, giving 18 × 5 = 90 mm bore. The 190 mm outside diameter and 43 mm width follow the ISO 15 diameter series, not the bore code alone.
What does no suffix on 6318 mean?
A bare 6318 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 90 mm bore?
The '3' is the medium diameter series: 190×43 mm, 50.0 mm radial section at 90 mm bore, carrying more load than a 6218 but needing a larger housing bore and giving up some speed.
What is the SKF designation and catalogue data for 6318?
In the SKF Rolling Bearings catalogue this size is listed as 6318 — the open (unsealed) execution, 90×190×43 mm per ISO 15. Quoted values: C 151 kN, C0 108 kN, Pu 3.8 kN, limiting speed 4800 r/min, mass 4950 g. Brand suffixes (2Z, 2RSH) differ from the industry-neutral spelling 6318.
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.