3318-A bearing: complete specifications & equivalents
The 3318-A is a ISO 15 radial bearing sized 90 x 190 x 73 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 90 mm |
| Outer diameter D | 190 mm |
| Width B | 73 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 208 kN |
| Basic static load rating C0 | 180 kN |
| Fatigue load limit Pu | 6.4 kN |
| Reference speed (thermal) | 3800 rpm |
| Limiting speed (mechanical) | 3400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 9250 g |
| Manufacturer designation | 3318 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 | 3.543 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 2.874 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 50 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) | 17 of 20 |
| Bore above smallest 3300-series size | 75 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3318 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
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 3318-A model number is decoded
3318 A is SKF's 90 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, 90×190×73 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 90×190×73 mm (3.543×7.48×2.874 in), 50.0 mm radial section height, C 208 kN, C0 180 kN, Pu 6.4 kN.reference speed 3,800 r/min (thermal) and limiting speed 3,400 r/min (mechanical), catalogue mass 9250 g. Mass and section check: 9250 g inside the 90×190×73 mm outline leaves a 50.0 mm radial section, and the 180 kN static rating is 0.87× the dynamic rating — plan static safety and minimum load against those numbers rather than against sister executions. Sizing arithmetic on the 90 mm bore: 208 kN C divided by the 50.0 mm radial section height gives 4.2 kN per section millimetre; the 9250 g mass and 3 % Pu/C share frame the light-load floor for the adjusted-life check. Speed-ratio note for this exact unit: the reference speed is 3,800 r/min against a 3,400 r/min limiting speed, i.e. a reference-to-limit ratio of 1.12.
Typical equipment & failure modes
Common applications
- process pump and agitator drives
- crane and winch gearboxes
- paper-machine dryer-section gearing
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
- rolling-contact fatigue spalling after the rated L10 life is exceeded
- electrical pitting on VFD-driven shafts without grounding protection
Selection pitfalls — read before you substitute
- 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.
- 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.
- Catalogue ratings of 208/180 kN apply to the A execution; the D and DNRCBM two-piece-ring executions carry their own figures on their own pages.
- 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.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3318 A as the double a steel execution; the other order numbers of the 3318 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 3318-A?
3318 A measures 90 mm bore × 190 mm OD × 73 mm width (3.543 × 7.48 × 2.874 in), mass about 9250 g. SKF 17000 ratings: C 208 kN, C0 180 kN, Pu 6.4 kN, reference speed 3,800 r/min (thermal) and limiting speed 3,400 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.
Why choose the double-row 3318 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.
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).
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.