3308-ATN9 bearing: complete specifications & equivalents
The 3308-ATN9 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 | polymer (PA66 glass-fibre reinforced) |
| 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 ATN9 |
| 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-A | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×36.5 mm envelope with catalogue ratings within 10 %; 3308 A is the stamped steel 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-ATN9 model number is decoded
3308 ATN9 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. glass-fibre reinforced PA66 cage, ball-centred (suffix TN9), with a 120 °C continuous-temperature ceiling. 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 ATN9: 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. At the printed limiting speed of 7,500 r/min the mean pitch diameter dm ≈ 65.0 mm implies a dn value around 488k mm·r/min; the 8,000 r/min reference speed is the thermal-planning figure under catalogue load. Bore-to-OD planning: OD 90 over bore 40 is a 2.25× step for this size, and the 36.5 mm width gives a bore/width ratio of 1.10; use these ratios when housing space around the 40 mm shaft is the first constraint.
Typical equipment & failure modes
Common applications
- elevator and hoist machinery
- printing and converting machinery
- gearbox input and output shafts with bidirectional thrust
Known failure patterns
- false brinelling on the loaded row while the shaft stands idle under vibration
- snap-ring groove or two-piece-ring damage when the D execution is pressed home through the wrong ring
- TN9 cage embrittlement in a hot gearbox position beyond the 120 °C polymer ceiling
- 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
- Interference goes on the rotating ring (about k5 at 40 mm bore); the wide 36.5 mm ring is sensitive to tilted seats, so check squareness before clamping.
- The D executions have a two-piece inner ring: mount both halves square to each other, never press on the outer ring, and keep the split faces clean during fitting.
- Interference goes on the rotating ring (about k5 at 40 mm bore); the wide 36.5 mm ring is sensitive to tilted seats, so check squareness before clamping.
- 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 ATN9 as the double atn9 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-ATN9?
3308 ATN9 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 ATN9 suffix mean?
A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. glass-fibre reinforced PA66 cage, ball-centred (suffix TN9), with a 120 °C continuous-temperature ceiling.
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.