31305-DF bearing: complete specifications & equivalents
The 31305-DF is a ISO 355 radial bearing sized 25 x 62 x 36.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 25 mm |
| Outer diameter D | 62 mm |
| Width B | 36.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 79.9 kN |
| Basic static load rating C0 | 80 kN |
| Fatigue load limit Pu | 8.65 kN |
| Reference speed (thermal) | 6700 rpm |
| Limiting speed (mechanical) | 11000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 550 g |
| Manufacturer designation | SKF 31305/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 | 0.984 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 1.437 in |
| ISO bore code | 05 |
| Radial section height (D−d)/2 | 18.5 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) | 1 of 35 |
| Bore above smallest matched-df-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 31305 | 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 31305-DF model number is decoded
Ordering number SKF 31305/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 25 mm shaft — one order number, one factory setting.On the SKF nameplate, 31305-DF reads as base 31305 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 36.5 mm overall width of 31305-DF is the axial space the pair occupies. The C0/C balance of the pair is about 1.00; combined with the 8.65 kN fatigue limit this frames a set sized for reversing combined load on a 25 mm shaft rather than for pure radial duty. Dimensional interchange map: within its boundary plan the 25×62×36.5 mm envelope of 31305-DF is fixed, so shoulder, spacer and seal drawings can be dimensioned straight from the catalogue table. Thermal behaviour of the pair: heat generated in the 25 mm bore cones flows along the shaft and changes the setting; the /DF clearance class is chosen for the catalogue speed range 6,700–11,000 r/min, so re-select the clearance class if the application runs hotter. Clamp the assembled pair axially through the cones — never through the rollers — and verify the 36.5 mm overall width against the catalogue value before final torquing of the shaft nut.
Typical equipment & failure modes
Common applications
- light-duty gearbox input/output shafts
- electric-motor pinion shafts
- steering knuckles and small differentials
- light-duty gearbox input/output shafts
Known failure patterns
- false brinelling on idle paired sets exposed to machine vibration
- 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
- fretting corrosion on a loose rotating shaft seat
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- Replace 31305-DF as a complete set: pairing a new bearing with a worn partner leaves the clearance undefined even when the designation matches.
- Setting is built into 31305-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 31305-DF as a complete set: pairing a new bearing with a worn partner leaves the clearance undefined even when the designation matches.
- The 79.9/80 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 31305/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 31305-DF?
The SKF 31305/DF is a matched pair of single-row tapered roller bearings in face-to-face (X) matched pair arrangement with 25 mm bore, 62 mm outer diameter and 36.5 mm overall width (0.984 × 2.441 × 1.437 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 79.9 kN, C0 80 kN, fatigue load limit Pu 8.65 kN, reference speed 6,700 r/min, limiting speed 11,000 r/min, mass about 0.55 kg.
What does the /DF suffix on 31305-DF mean?
The base 31305 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 31305-DF for one bearing or the pair?
They are for the complete matched pair: C 79.9 kN dynamic and C0 80 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 31305 table values.
Can 31305-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 25 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 25 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.