6308-2RS bearing: complete specifications & equivalents
The 6308-2RS is a ISO 15 radial bearing sized 40 x 90 x 23 mm (bore x OD x width) with 2RS 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 | 2RS |
| 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 |
| Limiting speed (mechanical) | 5000 rpm |
| Operating temperature | -30 to +110 °C |
| Mass | 640 g |
| Manufacturer designation | SKF 6308-2RSH |
| 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 6308-2RS
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
Contact-sealed execution: greased and sealed for life, no relubrication path. Grease life — not steel fatigue — usually sets the replacement interval; rising running temperature or noise near the end of service is the practical trigger.
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; catalogue load ratings differ by >10% — re-rate the application 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 (2RS 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 (2RS 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 | 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-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (2RS vs OPEN) — confirm sealing suits the duty. |
| 6308-RSR-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (2RS vs RSR) — confirm sealing suits the duty. |
| 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 (2RS vs ZZ) — confirm sealing suits the duty. |
| 6308-2RS-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-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (2RS vs OPEN) — confirm sealing suits the duty. |
| 6308-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope per ISO 15; seal variant differs (2RS vs RSR) — confirm sealing suits the duty. |
| 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 (2RS 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 6308-2RS 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 -2RS denotes two contact-type elastomer seals over a lifetime grease fill; the sealing lips add drag compared with open or shielded versions. 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 contact-seal catalogue number is 6308-2RSH (older text: -2RS1), mapped here from the industry-neutral -2RS spelling.
Typical equipment & failure modes
Common applications
- centrifugal pumps
- small gearboxes
- conveyors and drives
- agricultural equipment
Known failure patterns
- seal-lip hardening and loss of pre-grease in sustained high-temperature service
- grease-life expiry in the sealed-for-life cavity (no relubrication path)
- rolling-contact fatigue spalling after the rated L10 life is exceeded
- brinelling from static overload or hammering during mounting
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 6308-2RS; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
- The 63xx medium section at 40 mm bore gains dynamic rating through larger rolling elements on a 90 mm OD; the penalty is mass and a lower limiting speed than the 6208 — do not specify it for speed-critical shafts.
- Contact seals add drag and heat: 6308-2RS runs slower and cooler-limited than the open 6308; rubber lips are generally limited to roughly 80–110 °C continuous depending on grease, and C3 clearance is the common hot-duty choice.
- Heat is the enemy of the sealed 6308-2RS: sustained running near the lip temperature limit hardens the rubber, after which grease escapes and dirt tracks in — watch the housing temperature in hot drives.
- The housing bore for the 90 mm OD should be round within IT7; an oval bore pinches the outer ring of 6308-2RS and shows up later as two-point loaded raceway wear.
- 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 6308-2RS drags the lip and overheats it.
- SKF catalogues the contact-sealed version as 6308-2RSH (older printings may read -2RS1); it is shipped pre-greased and its 5000 r/min limiting speed is set by seal-lip drag and grease life versus the open bearing's 17000 r/min thermal reference speed. The single-seal catalogue number is 6308-RSH, used where one shaft side needs external relubrication.
- A one-seal execution 6308-RSH exists for arrangements that lubricate through the open side; fitting 6308-2RSH instead means lifetime grease and no external oil supply — mixing the two in the same shaft can starve the sealed position.
- 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 6308-2RS bearing?
A 6308-2RS 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 contact rubber seals and is normally pre-greased.
What lubrication does 6308-2RS need?
6308-2RS 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.
How does the 6308 bore code work?
The last two digits of 6308 are bore code 08, giving 08 × 5 = 40 mm bore. The 90 mm outside diameter and 23 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the 2RS suffix on 6308-2RS mean?
2RS means two contact elastomer seals, one each side, usually over a lifetime grease fill. Sealing against dust and moisture is better than ZZ shields, but the lip drag lowers the speed and temperature ceiling.
What is the SKF designation and catalogue data for 6308-2RS?
In the SKF Rolling Bearings catalogue this size is listed as 6308-2RSH — two contact elastomer seals over a lifetime grease fill, 40×90×23 mm per ISO 15. Quoted values: C 42.3 kN, C0 24 kN, Pu 1.02 kN, limiting speed 5000 r/min, mass 640 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6308-2RS.
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.