6308-RSR bearing: complete specifications & equivalents
The 6308-RSR is a ISO 15 radial bearing sized 40 x 90 x 23 mm (bore x OD x width) with RSR sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 23 mm |
| Material | GCr15 |
| Seal / shield | RSR |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 42.3 kN |
| Basic static load rating C0 | 24 kN |
| Fatigue load limit Pu | 1.02 kN |
| Reference speed (thermal) | 17000 rpm |
| Limiting speed (mechanical) | 8500 rpm |
| Operating temperature | -30 to +120 °C |
| Mass | 650 g |
| Manufacturer designation | SKF 6308-2RZ |
| 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 | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 0.906 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 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) | 15 of 40 |
| Bore above smallest 6300-series size | 38 mm |
Mounting, lubrication & life for 6308-RSR
Recommended fits & mounting
- Rotating inner ring on a 40 mm shaft: k5; housing bore H7 for normal stationary-load outer rings. Reverse the logic if the outer ring rotates.
- Fit by induction heating (max 120 °C) where practical — never drive the ring home through the rolling elements.
- Keep shaft and housing fillet radii below the bearing chamfer so the 23 mm-wide ring seats square on its shoulder.
Lubrication strategy
Non-contact low-drag seal lips retain the factory grease but are not liquid-tight. Treat as grease-for-life in light, dry duty; in dirty or wet positions plan replacement around contamination rather than fatigue.
Worked L10 life example (illustrative duty)
For ball bearings, L10h = (C/P)3 · 106 / (60·n). Taking an example radial equivalent load P = 3 kN at n = 1,500 r/min (a small belted motor duty — substitute the real equivalent load from the application calculation):
C = 42.3 kN → L10h ≈ 31,147 hours
Choosing a section at the same 40 mm bore
| Series | Open execution | OD × width | C (kN) | Limiting speed (r/min) |
|---|---|---|---|---|
| 60xx | 6008-FAG | 68 × 15 | 17.8 | 14,600 |
| 62xx | 6208-FAG | 80 × 18 | 31.5 | 13,600 |
| 63xx | 6308-FAG | 90 × 23 | 47.0 | 11,800 |
| 64xx | 6408-FAG | 110 × 27 | 68.0 | 9,500 |
| 618xx | 61808-FAG | 52 × 7 | 4.9 | 19,300 |
| 619xx | 61908-FAG | 62 × 12 | 14.5 | 15,800 |
| 160xx | 16008 | 68 × 9 | 12.6 | 15,200 |
A larger section is not a drop-in swap — OD and width change — and same-envelope seal variants are compared on the 40×90×23 envelope page. Match meaning, not the size chart alone: see what the cross-reference levels mean.
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6308-2RS-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant (RSR vs 2RS) and load ratings differ — confirm sealing and rating before substituting. |
| 6308-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant (RSR vs OPEN) and load ratings differ — confirm sealing and rating before substituting. |
| 6308-ZZ-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant (RSR vs ZZ) and load ratings differ — confirm sealing and rating before substituting. |
| 6308 | 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. |
| 6308-2RS-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (RSR vs 2RS) — confirm sealing suits the duty. |
| 6308-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (RSR vs OPEN) — confirm sealing suits the duty. |
| 6308-RSR-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. |
| 6308-ZZ-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (RSR vs ZZ) — confirm sealing suits the duty. |
| 6308-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (RSR vs 2RS) — confirm sealing suits the duty. |
| 6308-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (RSR vs OPEN) — confirm sealing suits the duty. |
| 6308-RSR-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. |
| 6308-ZZ-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (RSR vs ZZ) — confirm sealing suits the duty. |
| 7308 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| NU308 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| 308 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 308 shares the 40×90×23 mm envelope but catalogue C/C0 differ — envelope match only after a load check. |
| 308-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 308-2Z shares the 40×90×23 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 6308-RSR model number is decoded
In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6308 carries bore code 08 = 40 mm. Outside diameter 90 mm and width 23 mm come from the ISO 15 boundary-dimensions general plan. Suffix -RSR denotes two low-friction non-contact elastomer seals; they keep coarse debris out with minimal drag but are not liquid-tight. For normal-load mounting with a rotating inner ring on a 40 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. SKF's low-friction seal suffix is 2RSL/2RZ (this page's industry-neutral spelling is -RSR); catalogue number 6308-2RZ.
Typical equipment & failure modes
Common applications
- small gearboxes
- conveyors and drives
- agricultural equipment
- fans and blowers
Known failure patterns
- ingress of fine dust or moisture past the non-contact lip in dirty or wet duty (RSR is not liquid-tight)
- lip-lubricant starvation if the bearing runs dry for extended periods
- raceway smearing under marginal lubrication at start-up
- edge loading from shaft deflection or housing misalignment
Selection pitfalls — read before you substitute
- At a 40 mm bore, a shaft-seat burr or an overtight setscrew can score the thin inner ring of 6308-RSR; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
- The 63xx medium series gains rating at 40 mm bore through a 90 mm OD and 23 mm width; the heavier rolling elements also trade away some speed versus a 6208.
- The low-drag lip of 6308-RSR barely touches the inner ring; after long shelf storage the grease can separate, so rotate the rings by hand and confirm smooth, silent running before fitting.
- The non-contact lip of 6308-RSR does not retain a lifetime grease fill the way a contact seal does; confirm the regreasing interval for the 40 mm bore position before relying on it as sealed-for-life.
- Axial location must clamp the ring face, not the seal area: a shoulder or circlip bearing on the seal side of the 23 mm-wide ring of 6308-RSR drags the lip and overheats it.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 90 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6308-RSR.
- SKF catalogues the low-friction seal as 6308-2RZ (suffix -2RSL or -2RZ): a non-contact elastomer lip that runs near the open 8500 r/min limiting speed, closer to the open bearing's 17000 r/min reference than the contact-seal version. It keeps coarse debris out without the drag of a contact seal, but is not liquid-tight — use 2RSH for wet or fine-dust positions.
- The 42.3/24 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 6308-RSR bearing?
A 6308-RSR deep-groove ball bearing has a 40 mm bore, 90 mm outer diameter and 23 mm width (1.575 × 3.543 × 0.906 in), per ISO 15 boundary dimensions. It is fitted with two low-friction non-contact rubber seals.
What internal clearance does 6308-RSR have?
Unless a clearance suffix says otherwise, 6308-RSR 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 6308 and verify the residual clearance after mounting.
How should 6308-RSR be mounted?
Apply the mounting force to the ring being fitted: on a 40 mm shaft seat the press load must pass through the inner-ring face only. A fitting sleeve and an arbor press are normally sufficient at this size. Never strike the outer ring, the cage or the seals.
What lubrication does 6308-RSR need?
6308-RSR is supplied pre-greased for life and is not designed to be opened for relubrication; where a relubrication path is required, specify the open 6308 with a housing grease fitting instead.
What is the SKF designation and catalogue data for 6308-RSR?
In the SKF Rolling Bearings catalogue this size is listed as 6308-2RZ — two low-friction non-contact elastomer seals, 40×90×23 mm per ISO 15. Quoted values: C 42.3 kN, C0 24 kN, Pu 1.02 kN, limiting speed 8500 r/min, mass 650 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6308-RSR.
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.