3309-A bearing: complete specifications & equivalents
The 3309-A is a ISO 15 radial bearing sized 45 x 100 x 39.7 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 45 mm |
| Outer diameter D | 100 mm |
| Width B | 39.7 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 75 kN |
| Basic static load rating C0 | 53 kN |
| Fatigue load limit Pu | 2.24 kN |
| Reference speed (thermal) | 7500 rpm |
| Limiting speed (mechanical) | 6700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1250 g |
| Manufacturer designation | 3309 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 | 1.772 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 1.563 in |
| ISO bore code | 09 |
| Radial section height (D−d)/2 | 27.5 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) | 8 of 20 |
| Bore above smallest 3300-series size | 30 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3309-DNRCBM | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×39.7 mm envelope, but catalogue C/C0 differ between executions (75/53 kN vs 61.8/52 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3309-ATN9 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 45×100×39.7 mm envelope with catalogue ratings within 10 %; 3309 ATN9 is the glass-fibre PA66 cage, open arrangement execution of this size — boundary dimensions interchangeable, execution differs. |
| 3309-DMA | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 45×100×39.7 mm envelope, but catalogue C/C0 differ between executions (75/53 kN vs 79.3/69.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3309-A-2Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 45×100×39.7 mm envelope with catalogue ratings within 10 %; 3309 A-2Z is the stamped steel cage, shields (-2Z) execution of this size — boundary dimensions interchangeable, execution differs. |
| 3309-A-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 45×100×39.7 mm envelope with catalogue ratings within 10 %; 3309 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 3309-A model number is decoded
3309 A is SKF's 45 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, 45×100×39.7 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 45×100×39.7 mm (1.772×3.937×1.563 in), 27.5 mm radial section height, C 75 kN, C0 53 kN, Pu 2.24 kN.reference speed 7,500 r/min (thermal) and limiting speed 6,700 r/min (mechanical), catalogue mass 1250 g. The 2.24 kN fatigue load limit is the equivalent-load floor for long-life adjustment; with 75/53 kN ratings and 1250 g mass this execution carries about 1.67 kN of C per millimetre of bore. Mass and section check: 1250 g inside the 45×100×39.7 mm outline leaves a 27.5 mm radial section, and the 53 kN static rating is 0.71× 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 7,500 r/min against a 6,700 r/min limiting speed, i.e. a reference-to-limit ratio of 1.12.
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
- raceway staining from water in the lubricant during idle periods
- raceway staining from water in the lubricant during idle periods
Selection pitfalls — read before you substitute
- Catalogue ratings of 75/53 kN apply to the A execution; the D and DNRCBM two-piece-ring executions carry their own figures on their own pages.
- Interference goes on the rotating ring (about k5 at 45 mm bore); the wide 39.7 mm ring is sensitive to tilted seats, so check squareness before clamping.
- Interference goes on the rotating ring (about k5 at 45 mm bore); the wide 39.7 mm ring is sensitive to tilted seats, so check squareness before clamping.
- The double-row 3309 takes thrust in both directions by itself — that is the reason to choose it over two single-row bearings: one housing bore, one fit, built-in set geometry.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3309 A as the double a steel execution; the other order numbers of the 3309 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 3309-A?
3309 A measures 45 mm bore × 100 mm OD × 39.7 mm width (1.772 × 3.937 × 1.563 in), mass about 1250 g. SKF 17000 ratings: C 75 kN, C0 53 kN, Pu 2.24 kN, reference speed 7,500 r/min (thermal) and limiting speed 6,700 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.
Does the 3309 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 45 mm shaft and H7 in the 100 mm housing; check the wide ring seats square because the 39.7 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.