30318 bearing: complete specifications & equivalents
The 30318 is a ISO 355 radial bearing sized 90 x 190 x 46.5 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 | 46.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 353 kN |
| Basic static load rating C0 | 400 kN |
| Fatigue load limit Pu | 44 kN |
| Reference speed (thermal) | 2600 rpm |
| Limiting speed (mechanical) | 3600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 5650 g |
| Manufacturer designation | SKF 30318 |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB); 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 & 30300-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.831 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 50 mm |
| Smallest bore in 30300-series | 15 mm |
| Largest outer diameter in 30300-series | 500 mm |
| Width range across 30300-series | 14.25–105 mm |
| Bore position in 30300-series (smallest first) | 17 of 32 |
| Bore above smallest 30300-series size | 75 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30318 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 355 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 30318 model number is decoded
Ordering number SKF 30318 in SKF catalogue PUB BU/P1 17000 denotes a single-row tapered roller bearing for a 90 mm shaft, heavy-OD section, with an open pressed-steel-cage execution and one-direction axial capacity.On the SKF nameplate, 30318 follows the ISO 355 convention: 3 for the tapered-roller type, 03 for the heavy-OD section, final digits 18 for the 90 mm bore. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. 2GB); it is the dimensional series, not a separate part number. At 2,600 r/min reference speed the 50.0 mm-section 30318 is governed thermally by preload and lubricant flow; grease or oil selection should be made against that value, with 3,600 r/min as the mechanical ceiling. Mounting practice for 30318: the rotating cone takes the interference fit (k5 on a 90 mm shaft), the cup slides for axial location, and reversing-thrust duty demands a paired O/X set rather than one bearing.
Typical equipment & failure modes
Common applications
- marine deck machinery shafts
- heavy industrial gearboxes and speed reducers
- large process pump and compressor shafts
- rolling-mill auxiliary drives
Known failure patterns
- cup or cone misalignment when the separable rings are not seated square during mounting
- loose cup rotation in the housing when the specified press fit is not achieved
- roller large-end smearing against the cone rib after EP lubricant film failure
- false brinelling on idle paired sets exposed to machine vibration
- cage pocket scoring when the bearing starts cold with grease of too-high base-oil viscosity
- rib-roller contact scoring from loss of the EP additive film
Selection pitfalls — read before you substitute
- Mount the 90 mm bore 30318 by induction heating of the cone (max 120 °C — the pressed-steel cage sets the ceiling, not the steel); driving it home through the cup or rollers brinells the tapered raceway.
- The 303 series at 90 mm bore (190×46.5 mm) carries a larger OD and higher capacity than 30218 at the same bore; the bigger section runs hotter, so re-check the 3,600 r/min speed ceiling and shoulder diameters before substituting.
- A single 30318 cannot locate the shaft axially in both directions; mounting it singly on a reversing-thrust shaft leaves one direction uncontrolled — always use an O or X matched pair for bidirectional location.
- At the 353 kN rating of 30318, preload class changes stiffness by tens of percent but also heat generation; select light preload for the 3,600 r/min speed end and heavier preload only where moment stiffness dominates.
- Never press both rings through the wrong element during fitting: force for an interference shaft seat goes through the cone only, or brinell marks on the 190 mm cup race release as noise within the first running hours.
- The 353/400 kN ratings are SKF catalogue 17000 values for the basic execution; SKF can revise internal geometry without changing the order number, so keep the catalogue version (PUB BU/P1 17000/1 EN, 2018) with the specification and re-verify for critical drives.
- SKF lists several executions of 30318 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30318 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 30318?
The SKF 30318 is a single-row tapered roller bearing with 90 mm bore, 190 mm outer diameter and 46.5 mm width (3.543 × 7.48 × 1.831 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 353 kN, C0 400 kN, fatigue load limit Pu 44 kN, reference speed 2,600 r/min, limiting speed 3,600 r/min, mass about 5650 g. It is an open, separable bearing with a pressed-steel cage.
How does the 30318 bore code work?
The last two digits of 30318 are bore code 18, so 18 × 5 = 90 mm bore. The 190 mm OD and 46.5 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 30318 series and basic execution designations mean?
The leading 3 marks a single-row tapered roller bearing; the second digit 03 is the ISO 355 series (heavy-OD section). The SKF catalogue lists the ISO 355 dimension-series code after the bare number. A steeper-contact-angle variant (B suffix) is a different order number and is not interchangeable with the basic execution.
Can a single 30318 take axial load in both directions?
No — one single-row tapered roller bearing reacts thrust in one direction only, and under radial load its contact angle induces an axial force. Use two bearings as a matched pair: O (back-to-back) for a rigid, moment-resisting arrangement, X (face-to-face) where thermal expansion must be tolerated, or tandem where one-direction thrust is shared.
How does 30318 compare with a ball bearing of the same bore?
A tapered roller bearing has line contact and a steep contact angle: much higher combined axial-plus-radial capacity and shock resistance than a ball bearing of the same bore, at the cost of speed, one-direction thrust, mandatory pairing for reversing loads and a minimum axial load requirement. A ball bearing cannot be dropped into a combined-load 30318 position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB on 2026-09-26. Read our editorial & correction policy.