30306-DF bearing: complete specifications & equivalents
The 30306-DF is a ISO 355 radial bearing sized 30 x 72 x 41.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 30 mm |
| Outer diameter D | 72 mm |
| Width B | 41.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 119 kN |
| Basic static load rating C0 | 112 kN |
| Fatigue load limit Pu | 12.7 kN |
| Reference speed (thermal) | 6700 rpm |
| Limiting speed (mechanical) | 10000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 810 g |
| Manufacturer designation | SKF 30306/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 | 1.181 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 1.634 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 21 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) | 2 of 35 |
| Bore above smallest matched-df-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30306 | 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. |
| 30306-NTN | NTN | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Model-number interchange per ISO 15; confirm dimensions, sealing and ratings in the supplier catalogue. |
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 30306-DF model number is decoded
The code breaks down as base bearing 30306 plus matched-set suffix /DF: two bearings of the 30 mm bore size, paired face-to-face (X) matched pair, with the 41.5 mm overall width spanning the whole arrangement. Face-to-face matching puts the small rib ends outward, so the pressure cones cross inside the pair; 30306-DF therefore runs cooler where the shaft expands axially, at the price of lower moment stiffness than an O-arrangement of the same 30 mm bore. Selection arithmetic: the catalogue C 119 kN and C0 112 kN are ratings of the complete pair, not of one bearing — never halve them back to a single-row figure when checking L10 life, and use the pair Pu 12.7 kN as the fatigue floor. Material and manufacturing detail: the 810 g catalogue mass reflects through-hardened bearing steel machined to the listed envelope; ring roundness and width tolerance keep the mounted-setting scatter inside the catalogue class. Spacer discipline: the spacer between the two bearings of 30306-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. Lubrication for the pair should be sized against the combined 41.5 mm width and 810 g mass: two roller sets sweep twice the contact area of a single bearing of the same bore.In SKF catalogue PUB BU/P1 17000, 30306-DF appears as SKF 30306/DF: a matched face-to-face (X) matched pair pair for a 30 mm shaft, rated as a set at C 119 kN and C0 112 kN.
Typical equipment & failure modes
Common applications
- differential and pinion drives
- pump and compressor shafts
- machine-tool spindles
- machine-tool spindles
Known failure patterns
- axial overload spalling at the roller-rib contact beyond the single-row thrust rating
- 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
- hard-particle indentation of the tapered raceway in unfiltered oil
Selection pitfalls — read before you substitute
- A matched /DF set is ground as one system: never separate the two bearings of 30306-DF or swap the spacer — the factory clearance is lost the moment the set is broken.
- Setting is built into 30306-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 30306-DF as a complete set: pairing a new bearing with a worn partner leaves the clearance undefined even when the designation matches.
- The 119/112 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 30306/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 30306-DF?
The SKF 30306/DF is a matched pair of single-row tapered roller bearings in face-to-face (X) matched pair arrangement with 30 mm bore, 72 mm outer diameter and 41.5 mm overall width (1.181 × 2.835 × 1.634 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 119 kN, C0 112 kN, fatigue load limit Pu 12.7 kN, reference speed 6,700 r/min, limiting speed 10,000 r/min, mass about 0.81 kg.
What does the /DF suffix on 30306-DF mean?
The base 30306 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 30306-DF for one bearing or the pair?
They are for the complete matched pair: C 119 kN dynamic and C0 112 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 30306 table values.
Can 30306-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 30 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 30 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.