3311-ATN9 bearing: complete specifications & equivalents
The 3311-ATN9 is a ISO 15 radial bearing sized 55 x 120 x 49.2 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 49.2 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 112 kN |
| Basic static load rating C0 | 81.5 kN |
| Fatigue load limit Pu | 3.45 kN |
| Reference speed (thermal) | 5300 rpm |
| Limiting speed (mechanical) | 5300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2650 g |
| Manufacturer designation | 3311 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 | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.937 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 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) | 10 of 20 |
| Bore above smallest 3300-series size | 40 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3311-DNRCBM | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 55×120×49.2 mm envelope, but catalogue C/C0 differ between executions (112/81.5 kN vs 95.6/83 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3311-DMA | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 55×120×49.2 mm envelope, but catalogue C/C0 differ between executions (112/81.5 kN vs 111/100 kN) — boundary dimensions match, not a load-rating equivalent. |
| 3311-A | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 55×120×49.2 mm envelope with catalogue ratings within 10 %; 3311 A is the stamped steel cage, open arrangement execution of this size — boundary dimensions interchangeable, execution differs. |
| 3311-A-2Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 55×120×49.2 mm envelope with catalogue ratings within 10 %; 3311 A-2Z is the stamped steel cage, shields (-2Z) execution of this size — boundary dimensions interchangeable, execution differs. |
| 3311-A-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 55×120×49.2 mm envelope with catalogue ratings within 10 %; 3311 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 3311-ATN9 model number is decoded
3311 ATN9 is SKF's 55 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, 55×120×49.2 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 55×120×49.2 mm (2.165×4.724×1.937 in), 32.5 mm radial section height, C 112 kN, C0 81.5 kN, Pu 3.45 kN.reference speed 5,300 r/min (thermal) and limiting speed 5,300 r/min (mechanical), which coincide for this size, catalogue mass 2650 g. Speed planning distinguishes the two published ceilings mechanically: the cage and balls tolerate 5,300 r/min while thermal balance under catalogue load sets the 5,300 r/min reference; at dm ≈ 87.5 mm the corresponding dn is approximately 464k mm·r/min. Selection figures for 3311 ATN9: the static-to-dynamic ratio C0/C is 0.73, Pu 3.45 kN is about 3 % of C, and catalogue mass works out to roughly 48 g per millimetre of bore. Bore-to-OD planning: OD 120 over bore 55 is a 2.18× step for this size, and the 49.2 mm width gives a bore/width ratio of 1.12; use these ratios when housing space around the 55 mm shaft is the first constraint.
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
- 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 embrittlement in a hot gearbox position beyond the 120 °C polymer ceiling
- mounting score marks when the bearing is cocked over a burr or keyway
- hard-particle indentation of the asymmetric raceway in unfiltered oil
Selection pitfalls — read before you substitute
- Interference goes on the rotating ring (about k5 at 55 mm bore); the wide 49.2 mm ring is sensitive to tilted seats, so check squareness before clamping.
- Compared with a single-row pair of the same bore, the double-row 3311 occupies less axial space but offers less freedom to adjust preload — do not substitute without re-checking the arrangement.
- The double-row 3311 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 of 112/81.5 kN apply to the ATN9 execution; the D and DNRCBM two-piece-ring executions carry their own figures on their own pages.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3311 ATN9 as the double atn9 execution; the other order numbers of the 3311 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 3311-ATN9?
3311 ATN9 measures 55 mm bore × 120 mm OD × 49.2 mm width (2.165 × 4.724 × 1.937 in), mass about 2650 g. SKF 17000 ratings: C 112 kN, C0 81.5 kN, Pu 3.45 kN, reference speed 5,300 r/min (thermal) and limiting speed 5,300 r/min (mechanical), which coincide for this size.
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.
What does the D mean in ATN9?
D marks a two-piece inner ring, used on the heavy 33-series executions to simplify mounting; the rest of the suffix identifies the cage (MA brass outer-ring-centred, M brass ball-centred, J1 stamped steel, TN9 PA66) and snap-ring/clearance options (NR, CB).
Does the 3311 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.
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.