6318-ZZ bearing: complete specifications & equivalents
The 6318-ZZ is a ISO 15 radial bearing sized 90 x 190 x 43 mm (bore x OD x width) with ZZ sealing. 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 | ZZ |
| 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) | 3800 rpm |
| Operating temperature | -30 to +120 °C |
| Mass | 5150 g |
| Manufacturer designation | SKF 6318-2Z |
| 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 | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | ISO 15 boundary-dimension envelope; seal suffix convention varies by brand (2RS / DDU / LLU / 2RSR) — verify seal design and temperature range before substituting. |
| 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 (ZZ vs 2RS) — confirm sealing suits the duty. |
| 6318-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 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 (ZZ vs RSR) — confirm sealing suits the duty. |
| 6318-ZZ-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. |
| 6318-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 6318-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 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 (ZZ vs RSR) — confirm sealing suits the duty. |
| 6318-ZZ-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. |
| 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-ZZ model number is decoded
6318-ZZ carries two non-contact sheet-steel shields that hold the factory grease in and keep coarse debris out; they do not seal against liquids. Within the medium 63xx section (diameter series 3 of ISO 15), multiplying bore code 18 by five gives the 90 mm bore; the 190 mm outside diameter and 43 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 90 mm shaft under normal load, catalogue practice seats it on a k5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. SKF's own suffix is 2Z (this page's industry-neutral spelling is -ZZ); catalogue number 6318-2Z.
Typical equipment & failure modes
Common applications
- pulp and paper machinery
- medium and heavy industrial drives
- large gearboxes
- industrial fans and blowers
Known failure patterns
- fine-particle abrasion when non-contact shields let dust past in dirty duty
- grease aging in the shield-for-life cavity with no relubrication path
- brinelling from static overload or hammering during mounting
- false brinelling from vibration while the shaft is stationary
Selection pitfalls — read before you substitute
- Large bores like the 90 mm of 6318-ZZ demand clean, burr-free seats; one raised burr under a ring this size cocks the bearing and concentrates load at the raceway edge, cutting life drastically.
- 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.
- ZZ shields are non-contact: 6318-ZZ blocks chips and coarse dust but is not waterproof — do not install it expecting a pressure-wash seal, step up to 6318-2RS for that.
- Do not wash 6318-ZZ in solvent before mounting: the grease inside the shielded cavity is the service fill, and solvent creeping past the shield gap strips it out.
- 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-ZZ.
- Grease compatibility is not guaranteed between fills: mixing lithium and polyurea thickeners in a 6300-series position can soften the mixture and leak — clean out the old fill before switching grease types.
- SKF spells the shielded version 6318-2Z (one shield: 6318-Z), not "-ZZ": the suffix language differs by brand even though the ISO envelope is identical, so quote the brand designation when ordering.
- The single-shield execution 6318-Z is a distinct order number in catalogue 17000: it suits open gears or oil-bath arrangements where the unshielded face faces the lubricant, and it is not interchangeable with the double-shield 6318-2Z for high-contamination positions.
- 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-ZZ bearing?
A 6318-ZZ 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 fitted with two non-contact metallic shields.
What does the ZZ suffix on 6318-ZZ mean?
ZZ means two non-contact sheet-metal shields, one each side. They retain factory grease and block coarse particles with little friction, but do not seal against liquids, fine dust or pressure washing.
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.
Are 6318 bearings from different brands interchangeable?
For boundary dimensions, yes: every brand's 6318 uses the same ISO 15 envelope (90×190×43 mm). Load ratings, limiting speeds, clearance, precision class and sealing design can differ, so verify those in the supplier catalogue when substituting. Seal suffixes also differ by brand (2RS, DDU, LLU, 2RSL and similar).
What is the SKF designation and catalogue data for 6318-ZZ?
In the SKF Rolling Bearings catalogue this size is listed as 6318-2Z — two non-contact sheet-metal shields, 90×190×43 mm per ISO 15. Quoted values: C 151 kN, C0 108 kN, Pu 3.8 kN, limiting speed 3800 r/min, mass 5150 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6318-ZZ.
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.