30221-DF bearing: complete specifications & equivalents
The 30221-DF is a ISO 355 radial bearing sized 105 x 190 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 | 105 mm |
| Outer diameter D | 190 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 | 571 kN |
| Basic static load rating C0 | 710 kN |
| Fatigue load limit Pu | 80 kN |
| Reference speed (thermal) | 2200 rpm |
| Limiting speed (mechanical) | 3400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 9000 g |
| Manufacturer designation | SKF 30221/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 | 4.134 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 3.071 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 42.5 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) | 17 of 35 |
| Bore above smallest matched-df-series size | 80 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30221 | 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 30221-DF model number is decoded
Inspection shorthand: at overhaul, mark both bearings and the spacer of 30221-DF before disassembly — the set is a matched system, and re-assembling with one component reversed changes the factory setting. Clamp the assembled pair axially through the cones — never through the rollers — and verify the 78 mm overall width against the catalogue value before final torquing of the shaft nut.Ordering number SKF 30221/DF in SKF catalogue PUB BU/P1 17000 denotes two single-row tapered roller bearings supplied as a matched face-to-face (X) matched pair set for a 105 mm shaft — one order number, one factory setting.On the SKF nameplate, 30221-DF reads as base 30221 in a /DF matched execution — the suffix is part of the order number because a matched set is ground for a specific axial clearance and cannot be assembled from loose single bearings. 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 30221-DF is the axial space the pair occupies. With a pair mass of 9000 g across the 105×190×78 mm envelope, the set replaces what would otherwise be two separate bearings plus spacer grinding work — the factory setting is the engineering value being purchased. Operating context for the 105 mm bore: a shaft of this diameter typically runs in the large-bore band of industrial duty, and the 190 mm OD places the housing shoulder near 198 mm outer abutment.
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
- thermal preload runaway in an O-arrangement pair when inner-ring heat expands the setting
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- grease degradation after long shelf storage without rotation or re-greasing
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- A matched /DF set is ground as one system: never separate the two bearings of 30221-DF or swap the spacer — the factory clearance is lost the moment the set is broken.
- Setting is built into 30221-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.
- Spacer faces must stay parallel within the set's own tolerance; a tilted spacer in 30221-DF concentrates reversing thrust on one bearing and shows up as one-sided raceway wear.
- The 571/710 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 30221/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 30221-DF?
The SKF 30221/DF is a matched pair of single-row tapered roller bearings in face-to-face (X) matched pair arrangement with 105 mm bore, 190 mm outer diameter and 78 mm overall width (4.134 × 7.48 × 3.071 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 571 kN, C0 710 kN, fatigue load limit Pu 80 kN, reference speed 2,200 r/min, limiting speed 3,400 r/min, mass about 9.00 kg.
What does the /DF suffix on 30221-DF mean?
The base 30221 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 30221-DF for one bearing or the pair?
They are for the complete matched pair: C 571 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 30221 table values.
Can 30221-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 (m6 on a rotating 105 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 105 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.