3308-A bearing: complete specifications & equivalents
The 3308-A is a ISO 15 radial bearing sized 40 x 90 x 36.5 mm (bore x OD x width). 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 | 36.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 64 kN |
| Basic static load rating C0 | 44 kN |
| Fatigue load limit Pu | 1.86 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 7500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 930 g |
| Manufacturer designation | 3308 A |
| 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 & 3300-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 1.437 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 3300-series | 15 mm |
| Largest outer diameter in 3300-series | 240 mm |
| Width range across 3300-series | 19–92.1 mm |
| Bore position in 3300-series (smallest first) | 7 of 20 |
| Bore above smallest 3300-series size | 25 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3308-DNRCBM | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×36.5 mm envelope, but catalogue C/C0 differ between executions (64/44 kN vs 49.4/41.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-ATN9 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×36.5 mm envelope with catalogue ratings within 10 %; 3308 ATN9 is the glass-fibre PA66 cage, open arrangement execution of this size — boundary dimensions interchangeable, execution differs. |
| 3308-DMA | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×36.5 mm envelope, but catalogue C/C0 differ between executions (64/44 kN vs 68.9/57 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-DTN9 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×36.5 mm envelope, but catalogue C/C0 differ between executions (64/44 kN vs 68.9/57 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-A-2Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×36.5 mm envelope with catalogue ratings within 10 %; 3308 A-2Z is the stamped steel cage, shields (-2Z) execution of this size — boundary dimensions interchangeable, execution differs. |
| 3308-A-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×36.5 mm envelope with catalogue ratings within 10 %; 3308 A-2RS1 is the stamped steel cage, contact NBR seals (-2RS1) execution of this size — boundary dimensions interchangeable, execution differs. |
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 3308-A model number is decoded
3308 A is SKF's 40 mm-bore double-row angular-contact ball bearing of the 3300 series — two ball rows back-to-back for two-direction axial location in one unit, 40×90×36.5 mm. A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage. Envelope 40×90×36.5 mm (1.575×3.543×1.437 in), 25.0 mm radial section height, C 64 kN, C0 44 kN, Pu 1.86 kN.reference speed 8,000 r/min (thermal) and limiting speed 7,500 r/min (mechanical), catalogue mass 930 g. Selection figures for 3308 A: the static-to-dynamic ratio C0/C is 0.69, Pu 1.86 kN is about 3 % of C, and catalogue mass works out to roughly 23 g per millimetre of bore. Speed planning distinguishes the two published ceilings mechanically: the cage and balls tolerate 7,500 r/min while thermal balance under catalogue load sets the 8,000 r/min reference; at dm ≈ 65.0 mm the corresponding dn is approximately 488k mm·r/min. Speed-ratio note for this exact unit: the reference speed is 8,000 r/min against a 7,500 r/min limiting speed, i.e. a reference-to-limit ratio of 1.07.
Typical equipment & failure modes
Common applications
- two-direction thrust positions without room for a paired single-row set
- centrifugal pump shafts
- elevator and hoist machinery
Known failure patterns
- two-direction thrust overload concentrating load on one row and spalling its raceway
- loss of controlled axial clearance (CB) after thermal growth removes residual play
- stamped steel cage noise and pocket wear in marginal-lubrication starts, where a brass-cage execution would survive
- brinelling from pressing the ring home through the balls or from static overload
- edge loading from shaft deflection or housing misalignment
Selection pitfalls — read before you substitute
- Controlled axial clearance is the heart of the design: the A execution is produced to the standard double-row axial clearance; check residual clearance after mounting and at operating temperature.
- A capped 3308-2Z/-2RS1 execution of this envelope exists for sealed-for-life duty; an open double-row bearing needs application sealing and a defined lubricant supply.
- Compared with a single-row pair of the same bore, the double-row 3308 occupies less axial space but offers less freedom to adjust preload — do not substitute without re-checking the arrangement.
- A capped 3308-2Z/-2RS1 execution of this envelope exists for sealed-for-life duty; an open double-row bearing needs application sealing and a defined lubricant supply.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3308 A as the double a steel execution; the other order numbers of the 3308 size are different products and may carry different ratings — always quote the full designation when purchasing.
Frequently asked questions
What are the dimensions and catalogue data of 3308-A?
3308 A measures 40 mm bore × 90 mm OD × 36.5 mm width (1.575 × 3.543 × 1.437 in), mass about 930 g. SKF 17000 ratings: C 64 kN, C0 44 kN, Pu 1.86 kN, reference speed 8,000 r/min (thermal) and limiting speed 7,500 r/min (mechanical).
What does the A suffix mean?
A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage.
Which fits should I use?
With a rotating inner ring use roughly k5 on the 40 mm shaft and H7 in the 90 mm housing; check the wide ring seats square because the 36.5 mm width is sensitive to tilt.
Why choose the double-row 3308 instead of two single-row bearings?
The double-row bearing locates the shaft in both axial directions in one unit, in one housing bore and with factory-controlled axial clearance — a more compact arrangement than a pair, with no field matching of ground faces. A single-row pair offers adjustable preload instead.
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.