3311-A bearing: complete specifications & equivalents
The 3311-A 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 | steel, stamped ribbon (J-type) |
| 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 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 | 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-ATN9 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 55×120×49.2 mm envelope with catalogue ratings within 10 %; 3311 ATN9 is the glass-fibre PA66 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-A model number is decoded
3311 A 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. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage. 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. At the printed limiting speed of 5,300 r/min the mean pitch diameter dm ≈ 87.5 mm implies a dn value around 464k mm·r/min; the 5,300 r/min reference speed is the thermal-planning figure under catalogue load. Selection figures for 3311 A: 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. Speed-ratio note for this exact unit: the reference speed is 5,300 r/min against a 5,300 r/min limiting speed, i.e. a reference-to-limit ratio of 1.00.
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
- 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
- stamped steel cage noise and pocket wear in marginal-lubrication starts, where a brass-cage execution would survive
- edge loading from shaft deflection or housing misalignment
- brinelling from pressing the ring home through the balls or from static overload
Selection pitfalls — read before you substitute
- 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 A execution; the D and DNRCBM two-piece-ring executions carry their own figures on their own pages.
- 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.
- 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.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3311 A as the double a steel 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-A?
3311 A 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 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.
What does the D mean in A?
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.