C31-750-KMB bearing: complete specifications & equivalents
The C31-750-KMB is a ISO 15 radial bearing sized 750 x 1220 x 365 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 750 mm |
| Outer diameter D | 1220 mm |
| Width B | 365 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 16000 kN |
| Basic static load rating C0 | 30500 kN |
| Fatigue load limit Pu | 1800 kN |
| Reference speed (thermal) | 320 rpm |
| Limiting speed (mechanical) | 450 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1800000 g |
| Manufacturer designation | C 31/750 KMB |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings); 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 & C3100-series range
| Bore d | 29.528 in |
|---|---|
| Outer diameter D | 48.031 in |
| Width B | 14.37 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 235 mm |
| Smallest bore in C3100-series | 100 mm |
| Largest outer diameter in C3100-series | 1580 mm |
| Width range across C3100-series | 52–462 mm |
| Bore position in C3100-series (smallest first) | 27 of 28 |
| Bore above smallest C3100-series size | 650 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| C31-750-MB | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 750×1220×365 mm ISO 15 envelope and equivalent catalogue C/C0; C 31/750 MB is the cylindrical-bore MB inner-ring-guided brass-caged execution of this size — boundary dimensions interchangeable, only mounting and cage execution differ. |
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 C31-750-KMB model number is decoded
C 31/750 KMB belongs to the CARB family — compact aligning roller bearings: envelope 750×1220×365 mm, radial rating 16000/30500 kN C/C0, and no axial-locating function by design. The designation C 31/750 KMB separates into C (CARB), 31 (dimension series), 750 mm (slash-size) (750 mm bore — bore 750 mm is written directly after the slash) and KMB (tapered 1:12 bore for adapter (H) sleeve mounting, machined inner-ring-guided brass cage (MB)); envelope 750×1220×365 mm follows the ISO 15 plan. CARB bearings locate neither radially nor axially: the inner ring can walk axially inside the outer ring over the catalogue-listed axial-displacement range (s), so shaft thermal growth disappears as thrust rather than preloading the 750 mm seat. Speed planning separates the 320 r/min thermal reference from the 450 r/min mechanical limiting speed. The full-complement V executions carry more load but list no thermal reference speed; the brass-caged executions run faster and cooler at light load. After fitting, confirm the inner ring can be pushed axially by hand through the catalogue displacement range; a ring that will not slide means the position is locked and will preload in service.
Typical equipment & failure modes
Common applications
- continuous-caster guide rolls and slab-caster segments under heat growth
- vibrating screen exciters fitted with the VE240 tolerance execution
- long fan and kiln main shafts where the free end must float without thrust load
- heavy industrial gearbox layshafts used as the non-locating position
Known failure patterns
- raceway spalling once the catalogue L10 life is exceeded or after sustained overload
- edge loading and premature spalling when the CARB position is blocked from its designed axial float
- PA66 cage (TN9) softening when the sustained temperature passes the polymer limit
- brinelling of washer raceways from impact or mounting force applied through the rolling elements
- abrasive paste forming as dust bypasses the housing seals into the open washer set
Selection pitfalls — read before you substitute
- At 750 mm bore the 1800 kg mass and 365 mm width make seating geometry dominant: sphered-washer seats and oil flow must be verified in place, not just on the drawing.
- Do not block the axial displacement in the drawing: housing covers, labyrinth rings and snap rings must leave the catalogue float (s) free, or the bearing silently becomes a poorly located fixed bearing.
- Envelope-identical spherical roller bearings (same ISO 15 d×D×B) are not drop-in equivalents — they locate the shaft axially, while C 31/750 KMB must float; the two are designed to be used as a pair.
- Never use C 31/750 KMB as the locating bearing: it carries no axial load by design — the arrangement needs a separate locating spherical, tapered or angular bearing facing the thrust.
- Tapered-bore K executions mount on adapter sleeves (1:12) and K30 on withdrawal sleeves (1:30) — the 750 mm bore changes the sleeve family, and the drive-up procedure differs accordingly.
- The 16000/30500 kN ratings and 1800000 g mass are SKF catalogue values transcribed from ch. 10.1 of PUB BU/P1 17000 (PDF table page 868); mounting data — axial displacement (s) and seating details — appears in the running text because the structured record carries the boundary envelope only.
Frequently asked questions
Can a CARB bearing like C 31/750 KMB locate the shaft axially?
No — that is the defining feature. C 31/750 KMB deliberately allows the inner ring to float axially inside the outer ring while the toroidal rollers self-align. It must be paired with a separate locating bearing (spherical, tapered or angular contact) that takes 100 % of the thrust.
How is the C 31/750 KMB designation read?
C = CARB toroidal family; 31 = dimension series; 750 mm (slash-size) = 750 mm bore (the bore is written directly after the slash (no bore code)); suffix KMB selects tapered 1:12 bore for adapter (H) sleeve mounting, machined inner-ring-guided brass cage (MB). K is a 1:12 tapered bore for an adapter sleeve, K30 a 1:30 bore for a withdrawal sleeve.
What is the difference between V and TN9 CARB executions?
V is the full-complement execution with no cage — more rollers, higher C (16000 kN here) but a lower speed ceiling and no thermal reference speed. TN9 is the glass-fibre PA66 caged execution, faster and quieter at somewhat lower load. C 31/750 KMB is the tapered 1:12 bore for adapter (H) sleeve mounting, machined inner-ring-guided brass cage (MB).
How is C 31/750 KMB mounted?
The tapered 1:12 bore mounts on an adapter (H) sleeve with a defined drive-up; heat the bearing to max 120 °C when fitting, support full ring faces, and verify axial float afterwards.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings on 2026-09-27. Read our editorial & correction policy.