C31-750-MB bearing: complete specifications & equivalents
The C31-750-MB 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 MB |
| 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-KMB | 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 KMB is the 1:12 tapered-bore K 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-MB model number is decoded
C 31/750 MB is the dimension series 31 CARB toroidal roller bearings member of the CARB range: 750 mm bore, 1220 mm OD, 365 mm width, with the asymmetrical-looking toroidal roller set that defines the CARB principle. Reading the code: C marks the CARB toroidal family, the first two digits (31) identify the ISO dimension series and the last two (750 mm (slash-size)) encode the 750 mm bore; suffixes describe bore and execution. The cylindrical 750 mm bore mounts directly on a machined seat; the outer ring takes a loose housing fit so the bearing can float axially. The same size is listed in both bore executions, and the boundary dimensions 750×1220×365 mm are identical — only the mounting method changes. Selection arithmetic: C 16000 kN against C0 30500 kN gives a C0/C ratio of 1.91, and the 1800 kN fatigue load limit Pu sets the contamination-adjusted life floor. 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
- paper machine drying cylinders and calender rolls with long, thermally expanding shafts
- 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
Known failure patterns
- roller-end and flange smearing after lubricant starvation at the long roller contacts
- roller skew and cage damage after the bearing is clamped solid between shaft and housing shoulders
- brass cage pocket wear under marginal lubrication in the large-bore M/MB executions
- brinelling of washer raceways from impact or mounting force applied through the rolling elements
- grease churning and overheating when a high-speed thrust position is over-packed
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.
- 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.
- Reference and limiting speeds are different limits: the 320 r/min reference speed is the thermal criterion under load, the limiting value is the mechanical ceiling; observe the reference under load unless the arrangement calculation says otherwise.
- The quoted 16000/30500 kN ratings belong to this exact execution (C 31/750 MB); VE240 vibrating-screen variants and sealed 2CS/2NS variants have their own figures even at the same envelope.
- Never use C 31/750 MB 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.
- 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
Which dimensions does the C 31/750 MB have?
A C 31/750 MB measures 750 mm bore × 1220 mm outside diameter × 365 mm width (29.528 × 48.031 × 14.37 in). From SKF catalogue PUB BU/P1 17000: dynamic C 16000 kN, static C0 30500 kN, fatigue limit Pu 1800 kN, reference speed 320 r/min, limiting speed 450 r/min, mass about 1800000 g.
What does C 31/750 MB mean in SKF part numbering?
C marks CARB; 31 the dimension series; the size code gives 750 mm bore; MB is the execution (cylindrical bore for direct shaft fitting, machined inner-ring-guided brass cage (MB)). The envelope follows ISO 15 and matches spherical roller bearing outlines, but the functions differ.
Why is C 31/750 MB used opposite a spherical roller bearing?
The spherical bearing locates the shaft and takes thrust; the CARB bearing at the other end self-aligns but floats, absorbing thermal expansion without inducing axial load. The pair is standard on paper machine drying cylinders and long caster rolls.
Is the C 31/750 MB sealed?
No, it is an open execution relying on the housing seals; relubrication follows the groove/hole features of the size.
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.