3308-DTN9 bearing: complete specifications & equivalents
The 3308-DTN9 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 | 68.9 kN |
| Basic static load rating C0 | 57 kN |
| Fatigue load limit Pu | 2.45 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 7000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1050 g |
| Manufacturer designation | 3308 DTN9 |
| 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 (68.9/57 kN vs 49.4/41.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-A | 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 (68.9/57 kN vs 64/44 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-ATN9 | 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 (68.9/57 kN vs 64/44 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-DMA | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×36.5 mm envelope with catalogue ratings within 10 %; 3308 DMA is the brass cage, open arrangement execution of this size — boundary dimensions interchangeable, execution differs. |
| 3308-A-2Z | 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 (68.9/57 kN vs 64/44 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3308-A-2RS1 | 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 (68.9/57 kN vs 64/44 kN) — boundary dimensions match, not a load-rating equivalent. |
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-DTN9 model number is decoded
3308 DTN9 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. D marks a two-piece (split) inner ring that simplifies mounting of the heavy 33-series section. glass-fibre reinforced PA66 cage, ball-centred (suffix TN9), with a 120 °C continuous-temperature ceiling. DTN9 combines the split inner ring with the glass-fibre PA66 ball-centred TN9 cage. Envelope 40×90×36.5 mm (1.575×3.543×1.437 in), 25.0 mm radial section height, C 68.9 kN, C0 57 kN, Pu 2.45 kN.reference speed 8,000 r/min (thermal) and limiting speed 7,000 r/min (mechanical), catalogue mass 1050 g. Load balance: C0 57 kN against C 68.9 kN gives a 0.83 ratio, typical of a double-row bidirectional design; Pu 2.45 kN enters the SKF adjusted-life equation rather than the basic rating life. Mass and section check: 1050 g inside the 40×90×36.5 mm outline leaves a 25.0 mm radial section, and the 57 kN static rating is 0.83× the dynamic rating — plan static safety and minimum load against those numbers rather than against sister executions. Speed-ratio note for this exact unit: the reference speed is 8,000 r/min against a 7,000 r/min limiting speed, i.e. a reference-to-limit ratio of 1.14.
Typical equipment & failure modes
Common applications
- printing and converting machinery
- gearbox input and output shafts with bidirectional thrust
- two-direction thrust positions without room for a paired single-row set
Known failure patterns
- loss of controlled axial clearance (CB) after thermal growth removes residual play
- tilted mounting that loads one double row more heavily than the other
- TN9 cage damage when the split-ring bearing is heated above the PA66 ceiling during mounting
- electrical pitting on VFD-driven shafts without grounding protection
- raceway staining from water in the lubricant during idle periods
Selection pitfalls — read before you substitute
- 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.
- 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.
- 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.
- 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.
- 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.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3308 DTN9 as the double d tn9 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-DTN9?
3308 DTN9 measures 40 mm bore × 90 mm OD × 36.5 mm width (1.575 × 3.543 × 1.437 in), mass about 1050 g. SKF 17000 ratings: C 68.9 kN, C0 57 kN, Pu 2.45 kN, reference speed 8,000 r/min (thermal) and limiting speed 7,000 r/min (mechanical).
What does the DTN9 suffix mean?
A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. D marks a two-piece (split) inner ring that simplifies mounting of the heavy 33-series section. glass-fibre reinforced PA66 cage, ball-centred (suffix TN9), with a 120 °C continuous-temperature ceiling. DTN9 combines the split inner ring with the glass-fibre PA66 ball-centred TN9 cage.
Does the 3308 double-row bearing need pairing?
No — both ball rows are built into one bearing, so bidirectional location does not require a second unit. Controlled axial clearance is part of the design rather than a field adjustment.
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.
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.