C31-630-MB bearing: complete specifications & equivalents
The C31-630-MB is a ISO 15 radial bearing sized 630 x 1030 x 315 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 630 mm |
| Outer diameter D | 1030 mm |
| Width B | 315 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 11800 kN |
| Basic static load rating C0 | 20800 kN |
| Fatigue load limit Pu | 1290 kN |
| Reference speed (thermal) | 400 rpm |
| Limiting speed (mechanical) | 560 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1090000 g |
| Manufacturer designation | C 31/630 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 | 24.803 in |
|---|---|
| Outer diameter D | 40.551 in |
| Width B | 12.402 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 200 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) | 24 of 28 |
| Bore above smallest C3100-series size | 530 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| C31-630-KMB | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 630×1030×315 mm ISO 15 envelope and equivalent catalogue C/C0; C 31/630 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 C31-630-MB model number is decoded
For long shafts that grow thermally, SKF supplies C 31/630 MB: the toroidal rollers allow the 630 mm inner ring to displace axially without induced thrust, while still accommodating shaft deflection like a spherical bearing. SKF builds the CARB order number from size plus execution: the bare number C 31/630 is the brass-caged cylindrical-bore bearing, K (or K30) makes the bore tapered for sleeve mounting, and the cage/seal letters follow — here MB. The cylindrical 630 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 630×1030×315 mm are identical — only the mounting method changes. The 1090000 g mass over the 630×1030×315 mm envelope yields about 18.73 kN dynamic per millimetre of bore — the long toroidal rollers give this family its radial capacity density. Mounting: slide the bearing onto the 630 mm seat or heat it (max 120 °C) and seat it square; never press through the 315 mm roller set, and leave the free-end housing shoulder clear so axial float is unrestricted.
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
- roller-end and flange smearing after lubricant starvation at the long roller contacts
- edge loading and premature spalling when the CARB position is blocked from its designed axial float
- brass cage pocket wear under marginal lubrication in the large-bore M/MB executions
- electrical erosion of raceways on VFD-driven shafts without grounding or insulation
- abrasive paste forming as dust bypasses the housing seals into the open washer set
Selection pitfalls — read before you substitute
- At 630 mm bore the 1090 kg mass and 315 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 630 mm bore changes the sleeve family, and the drive-up procedure differs accordingly.
- Reference and limiting speeds are different limits: the 400 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 11800/20800 kN ratings belong to this exact execution (C 31/630 MB); VE240 vibrating-screen variants and sealed 2CS/2NS variants have their own figures even at the same envelope.
- 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.
- The 11800/20800 kN ratings and 1090000 g mass are SKF catalogue values transcribed from ch. 10.1 of PUB BU/P1 17000 (PDF table page 866); 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
What does C 31/630 MB mean in SKF part numbering?
C marks CARB; 31 the dimension series; the size code gives 630 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 31/630 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 31/630 MB sealed?
No, it is an open execution relying on the housing seals; relubrication follows the groove/hole features of the size.
What fails first on a misapplied CARB bearing?
Blocking the designed axial float — clamping the free end or locating both shaft ends — turns thermal growth into edge loading and spalls the toroidal raceways. Cage damage and ordinary fatigue follow overload or dry running.
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.