318 bearing: complete specifications & equivalents
The 318 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 |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 157 kN |
| Basic static load rating C0 | 160 kN |
| Fatigue load limit Pu | 5.7 kN |
| Reference speed (thermal) | 6300 rpm |
| Limiting speed (mechanical) | 4000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 5400 g |
| Manufacturer designation | 318 |
| 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 & 300-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 300-series | 25 mm |
| Largest outer diameter in 300-series | 190 mm |
| Width range across 300-series | 17–43 mm |
| Bore position in 300-series (smallest first) | 14 of 14 |
| Bore above smallest 300-series size | 65 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6318-RSR | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | NSK bearing NSK 6318VV on the same 90×190×43 mm envelope, but catalogue C/C0 differ (157/160 kN vs 157/107 kN) — envelope interchange only after a load check. |
| 6318-M | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×190×43 mm envelope as SKF 6318 M, but catalogue C/C0 differ (157/160 kN vs 151/108 kN) — envelope match only after a load check. |
| 318-ZZ | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 90×190×43 mm envelope and equivalent catalogue ratings; 318-2Z is the two non-contact shields execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| 6318 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6318 shares the 90×190×43 mm envelope but catalogue C/C0 differ (157/160 kN vs 151/108 kN) — envelope match, not a load-rating equivalent. |
| 6318-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6318-2Z shares the 90×190×43 mm envelope but catalogue C/C0 differ (157/160 kN vs 151/108 kN) — envelope match, not a load-rating equivalent. |
| 6318-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6318-2RS1 shares the 90×190×43 mm envelope but catalogue C/C0 differ (157/160 kN vs 151/108 kN) — envelope match, not a load-rating equivalent. |
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 318 model number is decoded
318 is a filling-slot (notched-ring) deep-groove bearing in the legacy 300-series: the last two digits encode the bore: 318 carries code 18 = 90 mm (code × 5). The rings carry loading slots that allow extra balls during assembly, which is what gives the 90×190×43 mm envelope its C 157 kN and C0 160 kN ratings (Pu 5.7 kN). The open 318 carries no shields or seals and relies on application lubrication and external sealing. Limiting speed 4000 r/min, mass 5400 g. These bearings are built for high purely-radial loads at moderate speeds.
Typical equipment & failure modes
Common applications
- slew drives
- material-handling winches
- slow heavy gearboxes
- farm machinery and harvesters
Known failure patterns
- spalling of the filling-slot edge when balls are hammered through the slot under heavy thrust loading
- dirt entering through the open slot area when external sealing is neglected
- raceway smearing under marginal lubrication at start-up
- electrical pitting in VFD-driven motors without shaft grounding
Selection pitfalls — read before you substitute
- Filling-slot bearings take heavy purely-radial load at moderate speed but little thrust; the 157/160 kN ratings assume radial loading — use deep-groove 6xxx where axial load matters.
- Shields on 318 retain grease but do not seal against water; for wet farm duty add external lip seals rather than trusting the shield.
- Limiting speed is just 4000 r/min: filling-slot cages and the slot geometry run cooler below that — overspeed drives cage wear and smearing.
- Filling slots let more balls be packed into the 90×190 mm envelope, which is why 318 reaches C 157 kN — but the slots also mean the two rings separate when the balls align with them, so handle it as a loose-clearance design.
- The slots sit at one angular position: on 318, never pass the full radial load across the slot zone during mounting or the ring lip can crack.
- Fillet radii must clear the 318 chamfer so the 43 mm-wide ring seats square; an oversized shaft radius creates point contact on the ring face.
Frequently asked questions
What are the dimensions of 318?
Filling-slot bearing 318 measures 90×190×43 mm (3.543×7.48×1.693 in), about 5400 g.
What does the designation 318 mean?
It is the legacy 200/300 filling-slot numbering: series 300 and bore code 18 = 90 mm. Filling-slot bearings predate the 6xxx deep-groove spelling.
What is a filling-slot bearing?
The inner and outer rings each have a loading slot; when aligned, extra balls can be inserted, raising radial rating (C 157 kN for 318). The slots also make the rings separable.
Can 318 take axial load?
Very little: the filling slots interrupt the raceway shoulders, so thrust towards the open slot side can unload or jam the balls. Use a standard deep-groove 6xxx bearing for combined loads.
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.