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 |
|---|---|
| Brand | SKF |
| 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 | 2026-09-25 |
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 | 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 | 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) | 25 of 40 |
| Bore above smallest 6300-series size | 88 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; standard interchange — confirm clearance class and precision with the supplier. |
| 6318-2RS-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6318-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. |
| 6318-RSR | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (OPEN vs RSR) — confirm sealing suits the duty. |
| 6318-ZZ-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 6318-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6318-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. |
| 6318-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (OPEN vs RSR) — confirm sealing suits the duty. |
| 6318-ZZ-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 7318 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| NU318 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| 21318 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| 6318-M | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 6318 M (machined brass cage, open arrangement) is the same-size execution on the 90×190×43 mm envelope with ratings within 10 % — boundary dimensions interchangeable. |
| 318 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 318 shares the 90×190×43 mm envelope but catalogue C/C0 differ — envelope match only after a load check. |
| 318-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 318-2Z shares the 90×190×43 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 6318 model number is decoded
In the 6300-series (diameter series 3 of ISO 15) 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
- medium and heavy industrial drives
- large gearboxes
- industrial fans and blowers
- hoists and winches
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- edge loading from shaft deflection or housing misalignment
- rolling-contact fatigue spalling after the rated L10 life is exceeded
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 section at 90 mm bore gains dynamic rating through larger rolling elements on a 190 mm OD; the penalty is mass and a lower limiting speed than the 6218 — do not specify it for speed-critical shafts.
- Storage matters for open bearings: 6318 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.
- 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.
- Axial location must clamp the ring face, not the seal area: a shoulder or circlip bearing on the seal side of the 43 mm-wide ring of 6318 drags the lip and overheats it.
- A 90 mm bore listing showing the right d/D/B but no standard or precision-class reference may be a loose-tolerance import; measure bore/OD spread before fitting it to a machined shaft.
- 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.
What internal clearance does 6318 have?
Unless a clearance suffix says otherwise, 6318 is manufactured to normal (CN) radial internal clearance. Tight fits and hot shafts consume clearance in service — for those conditions order the C3 execution of 6318 and verify the residual clearance after mounting.
How should 6318 be mounted?
Apply the mounting force to the ring being fitted: on a 90 mm shaft seat the press load must pass through the inner-ring face only. Induction heating of the inner ring (max 120 °C) is the clean method at this size. Never strike the outer ring, the cage or the seals.
What lubrication does 6318 need?
The open 6318 is lubricated by the application; a NLGI 2 lithium-soap grease filled to roughly 25–35% of the free volume is the common choice, with a defined relubrication interval.
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, 2RSL) 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 2026-09-25. Read our editorial & correction policy.