618-8 bearing: complete specifications & equivalents
The 618-8 is a ISO 15 radial bearing sized 8 x 16 x 4 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 8 mm |
| Outer diameter D | 16 mm |
| Width B | 4 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 0.819 kN |
| Basic static load rating C0 | 0.3 kN |
| Fatigue load limit Pu | 0.012 kN |
| Reference speed (thermal) | 90000 rpm |
| Limiting speed (mechanical) | 56000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3 g |
| Manufacturer designation | 618/8 |
| 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 & 61800-series range
| Bore d | 0.315 in |
|---|---|
| Outer diameter D | 0.63 in |
| Width B | 0.157 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 4 mm |
| Smallest bore in 61800-series | 1 mm |
| Largest outer diameter in 61800-series | 1820 mm |
| Width range across 61800-series | 1–140 mm |
| Bore position in 61800-series (smallest first) | 9 of 74 |
| Bore above smallest 61800-series size | 7 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| W618-8 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 8×16×4 mm envelope, but the stainless and chrome-steel executions carry different catalogue ratings (0.819/0.3 kN vs 0.715/0.3 kN) — envelope match, not a load-rating equivalent; choose by corrosion versus load duty. |
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 618-8 model number is decoded
In the miniature 61800-series, the bore is written directly after the slash as 8 mm (bores below 10 mm use the slash spelling). The envelope is 8×16×4 mm (0.315×0.63×0.157 in) with a 4.0 mm radial section height, C 0.819 kN, C0 0.3 kN and Pu 0.012 kN. The open 618/8 carries no shields or seals and relies on application lubrication and external sealing. Limiting speed 56000 r/min, catalogue mass 3 g. A thin section saves space but leaves little margin for misalignment or shaft deflection.
Typical equipment & failure modes
Common applications
- industrial fans
- compressor drives
- machine tool auxiliaries
- agricultural gearboxes
Known failure patterns
- contamination wear when the open arrangement is used without external seals
- lubricant starvation where no regreasing interval is maintained
- edge loading from shaft deflection or housing misalignment
- rolling-contact fatigue spalling once the catalogue L10 life is exceeded
Selection pitfalls — read before you substitute
- Fillet radii must clear the 618-8 chamfer so the 4 mm-wide ring seats square; an oversized shaft radius creates point contact on the ring face.
- Mount by heating the inner ring (max 120 °C) — driving 618-8 home through the outer ring or balls brinells the raceways.
- Open 618-8 needs external sealing at the arrangement level; in dusty housings its life depends entirely on those external seals and the regreasing schedule.
- Plan a relubrication interval for 618-8; run-to-failure on open deep-groove bearings is the dominant early-failure cause.
- Mount by heating the inner ring (max 120 °C) — driving 618-8 home through the outer ring or balls brinells the raceways.
- The fatigue load limit is 0.012 kN; it feeds the equivalent-mean-load check, not the basic life calculation — do not substitute one for the other.
Frequently asked questions
What are the dimensions of 618-8?
The SKF 618/8 measures 8 mm bore × 16 mm OD × 4 mm width (0.315 × 0.63 × 0.157 in), mass about 3 g. It is open, with no shields or seals.
Why is there a slash in the designation 618/8?
The slash writes a bore that falls outside the two-digit code table: 618/8 means 8 mm bore. The site slug 618-8 replaces the slash with a hyphen.
What is the speed rating of 618-8?
SKF lists a 90000 r/min thermal reference speed and a 56000 r/min mechanical limiting speed for 618/8; real limits also depend on lubrication and fits.
What is the difference between 618-8 and a same-bore 62-series bearing?
Section height differs: 618-8 has a 4 mm radial section and C 0.819 kN; always match d, D and B — same bore alone never makes two bearings interchangeable.
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.