31324X-DF bearing: complete specifications & equivalents
The 31324X-DF is a ISO 355 radial bearing sized 120 x 260 x 136 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 120 mm |
| Outer diameter D | 260 mm |
| Width B | 136 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 992 kN |
| Basic static load rating C0 | 1400 kN |
| Fatigue load limit Pu | 146 kN |
| Reference speed (thermal) | 1400 rpm |
| Limiting speed (mechanical) | 2400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 32500 g |
| Manufacturer designation | SKF 31324 X/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 | 4.724 in |
|---|---|
| Outer diameter D | 10.236 in |
| Width B | 5.354 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 70 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) | 19 of 35 |
| Bore above smallest matched-df-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 31324X | 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 31324X-DF model number is decoded
Dividing the pair C 992 kN by the 120 mm bore gives 8.27 kN per millimetre of journal for the complete arrangement — a density metric that compares matched sets across the face-to-face (X) matched pair family. Journal and housing interface: the 120 mm bore takes a m6 shaft seat and the 260 mm outside diameter pairs with an H7 housing bore; the 136 mm width defines shoulder depth and the 32500 g mass is the dead load in thermal-growth calculations. Thermal behaviour of the pair: heat generated in the 120 mm bore cones flows along the shaft and changes the setting; the /DF clearance class is chosen for the catalogue speed range 1,400–2,400 r/min, so re-select the clearance class if the application runs hotter. Do not separate 31324X-DF into single-bearing service stock — as individual bearings the components are not interchangeable with catalogue single-row executions because the rings are ground for the set.In SKF catalogue PUB BU/P1 17000, 31324X-DF appears as SKF 31324 X/DF: a matched face-to-face (X) matched pair pair for a 120 mm shaft, rated as a set at C 992 kN and C0 1400 kN.On the SKF nameplate, 31324X-DF reads as base 31324 X 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 136 mm overall width of 31324X-DF is the axial space the pair occupies.
Typical equipment & failure modes
Common applications
- large industrial mixer shafts
- offshore winch and drawworks drums
- rolling-mill roll-neck bearings
- marine propulsion gearboxes
Known failure patterns
- roller large-end smearing against the cone rib after EP lubricant film failure
- preload loss as the mounted pair relaxes, letting rollers skid and smear the raceways
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- electrical pitting on VFD-driven shafts without grounding protection
- 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 31324X-DF or swap the spacer — the factory clearance is lost the moment the set is broken.
- Spacer faces must stay parallel within the set's own tolerance; a tilted spacer in 31324X-DF concentrates reversing thrust on one bearing and shows up as one-sided raceway wear.
- A matched /DF set is ground as one system: never separate the two bearings of 31324X-DF or swap the spacer — the factory clearance is lost the moment the set is broken.
- The 992/1400 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 31324 X/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 31324X-DF?
The SKF 31324 X/DF is a matched pair of single-row tapered roller bearings in face-to-face (X) matched pair arrangement with 120 mm bore, 260 mm outer diameter and 136 mm overall width (4.724 × 10.236 × 5.354 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 992 kN, C0 1400 kN, fatigue load limit Pu 146 kN, reference speed 1,400 r/min, limiting speed 2,400 r/min, mass about 32.50 kg.
What does the /DF suffix on 31324X-DF mean?
The base 31324 X 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 31324X-DF for one bearing or the pair?
They are for the complete matched pair: C 992 kN dynamic and C0 1400 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 31324 X table values.
Can 31324X-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 120 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 120 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.