33018 bearing: complete specifications & equivalents
The 33018 is a ISO 355 radial bearing sized 90 x 140 x 39 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 | 140 mm |
| Width B | 39 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 266 kN |
| Basic static load rating C0 | 355 kN |
| Fatigue load limit Pu | 39 kN |
| Reference speed (thermal) | 3600 rpm |
| Limiting speed (mechanical) | 4500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2200 g |
| Manufacturer designation | SKF 33018 |
| 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 & 33000-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 5.512 in |
| Width B | 1.535 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 33000-series | 50 mm |
| Largest outer diameter in 33000-series | 225 mm |
| Width range across 33000-series | 24–59 mm |
| Bore position in 33000-series (smallest first) | 9 of 16 |
| Bore above smallest 33000-series size | 40 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 33018 | 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 33018 model number is decoded
The SKF 33018 is a 90×140×39 mm single-row tapered roller bearing — the slim light section entry in the 33000 series, with an asymmetric raceway cut for thrust capacity and separable mounting.Numbering ties the bearing to its envelope: 33018 means tapered-roller type 3, slim light section series 30, 90 mm bore — which is why the 140×39 mm outline swaps dimensionally with other ISO 355 bearings of the same code. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. 2CE); it is the dimensional series, not a separate part number. With C 266 kN and C0 355 kN, the 33018 pair-sizing check is dominated by the axial share: keep the equivalent load P below the rating at the required L10, remembering one bearing alone cannot cover reversing thrust at 4,500 r/min. Mounting practice for 33018: 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
- crane sheave and hoist gearboxes
- paper-machine and printing rolls
- construction machinery drives
- marine deck machinery shafts
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
- false brinelling on idle paired sets exposed to machine vibration
- roller large-end smearing against the cone rib after EP lubricant film failure
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- Mount the 90 mm bore 33018 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 330 series at 90 mm bore (140×39 mm) is the slim-OD envelope: it buys radial space but gives up capacity against a 30218 of the same bore — confirm the L10 margin before downsizing into it.
- Setting is a design value, not an assembly feel: excessive preload in the 33018 pair raises operating temperature and can trigger thermal runaway, while too little lets the rollers skid and smear the raceway under light load.
- When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 33018 pushes the rings apart under load, so a non-located cup walks its seat even when the shaft is fixed.
- Open 33018 units need application-supplied sealing and a defined EP lubricant supply; the roller-rib contact is the first to fail when the additive film breaks down.
- The 266/355 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 33018 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 33018 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 33018?
The SKF 33018 is a single-row tapered roller bearing with 90 mm bore, 140 mm outer diameter and 39 mm width (3.543 × 5.512 × 1.535 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 266 kN, C0 355 kN, fatigue load limit Pu 39 kN, reference speed 3,600 r/min, limiting speed 4,500 r/min, mass about 2200 g. It is an open, separable bearing with a pressed-steel cage.
How does the 33018 bore code work?
The last two digits of 33018 are bore code 18, so 18 × 5 = 90 mm bore. The 140 mm OD and 39 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 33018 series and basic execution designations mean?
The leading 3 marks a single-row tapered roller bearing; the second digit 30 is the ISO 355 series (slim light 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 33018 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 33018 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 33018 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.