33018-DF bearing: complete specifications & equivalents
The 33018-DF is a ISO 355 radial bearing sized 90 x 140 x 78 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 | 78 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 457 kN |
| Basic static load rating C0 | 710 kN |
| Fatigue load limit Pu | 78 kN |
| Reference speed (thermal) | 3000 rpm |
| Limiting speed (mechanical) | 4500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 4500 g |
| Manufacturer designation | SKF 33018/DF |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants |
| Last verified | 2026-09-29 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants) · extracted 2026-09-29
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants); 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 & matched-df-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 5.512 in |
| Width B | 3.071 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in matched-df-series | 25 mm |
| Largest outer diameter in matched-df-series | 540 mm |
| Width range across matched-df-series | 34.5–280 mm |
| Bore position in matched-df-series (smallest first) | 14 of 35 |
| Bore above smallest matched-df-series size | 65 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 33018 | 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 33018-DF model number is decoded
Spacer discipline: the spacer between the two bearings of 33018-DF is ground to the individual set — it carries a serial link to the pair, so never swap spacers between sets of the same designation. The rotating cones of 33018-DF take a k5 seat on the 90 mm shaft; the cups are a transition-to-loose fit so the pair can be clamped to its factory setting during assembly.For a 90 mm shaft carrying reversing axial load, SKF lists 33018-DF under catalogue execution SKF 33018/DF: a factory-matched face-to-face (X) matched pair tapered-roller pair, set and measured as one unit.Digit by digit, 33018-DF reads as the ISO 355 base bearing 33018 supplied as a face-to-face (X) matched pair matched pair (/DF); the 90 mm bore and 140 mm OD are per-bearing, the 78 mm width is for the set. In the face-to-face (X) arrangement the load lines of the two bearings converge toward the shaft axis: the set tolerates shaft deflection and thermal growth better than a back-to-back pair, but is less stiff against overturning moments. The 78 mm overall width of 33018-DF is the axial space the pair occupies. Catalogue mass 4500 g covers both bearings and the ground spacer of 33018-DF; keep the set complete — substituting one bearing or a non-ground spacer destroys the factory clearance. Assembly datum check: verify the 78 mm width against the drawing before clamping — the width is the assembled result and the quickest field check that the correct execution of 33018-DF is on the shaft.
Typical equipment & failure modes
Common applications
- paper-machine and printing rolls
- construction machinery drives
- marine deck machinery shafts
- heavy industrial gearboxes and speed reducers
Known failure patterns
- preload loss as the mounted pair relaxes, letting rollers skid and smear the raceways
- axial overload spalling at the roller-rib contact beyond the single-row thrust rating
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- rib-roller contact scoring from loss of the EP additive film
- fretting corrosion on a loose rotating shaft seat
Selection pitfalls — read before you substitute
- O and X arrangements are not interchangeable by turning the set around: 33018-DF in face-to-face (X) matched pair arrangement has its load-line geometry fixed — specify the arrangement from the shaft thermal and stiffness analysis.
- Setting is built into 33018-DF; the classic field error is re-adjusting a matched pair as if it were two loose single bearings, which destroys the /DF clearance class.
- Replace 33018-DF as a complete set: pairing a new bearing with a worn partner leaves the clearance undefined even when the designation matches.
- The 457/710 kN ratings are SKF catalogue 17000 values for this 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.
- Quote the full SKF 33018/DF designation when purchasing — base-number-only orders are ambiguous across executions and variants.
Frequently asked questions
What are the dimensions and catalogue data of 33018-DF?
The SKF 33018/DF is a matched pair of single-row tapered roller bearings in face-to-face (X) matched pair arrangement with 90 mm bore, 140 mm outer diameter and 78 mm overall width (3.543 × 5.512 × 3.071 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 457 kN, C0 710 kN, fatigue load limit Pu 78 kN, reference speed 3,000 r/min, limiting speed 4,500 r/min, mass about 4.50 kg.
What does the /DF suffix on 33018-DF mean?
The base 33018 is the ISO 355 single-row bearing; the /DF suffix marks the matched-set execution — the arrangement (face-to-face (X)), the ground spacer and the factory-set axial clearance class. A matched set cannot be assembled from loose single bearings; quote the full designation when ordering.
Are the C and C0 ratings of 33018-DF for one bearing or the pair?
They are for the complete matched pair: C 457 kN dynamic and C0 710 kN static already include load sharing between the two bearings. Do not halve them for single-bearing checks, and do not compare them directly with the single-row 33018 table values.
Can 33018-DF be adjusted like two loose tapered bearings?
No — the axial clearance is set at the factory by selective spacer grinding. Mounting work is limited to clean seats, correct fits (k5 on a rotating 90 mm shaft) and axial clamping through the cones; re-setting in the field destroys the matched clearance class.
When should a face-to-face (X) matched set be chosen?
Choose the face-to-face (X) set where the shaft grows thermally or alignment is imperfect — the converging load lines tolerate deflection. It is the default choice for wheel hubs and general gearbox shafts at the 90 mm bore.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants on 2026-09-29. Read our editorial & correction policy.