C31-630-KMB bearing: complete specifications & equivalents
The C31-630-KMB 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 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 | 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-MB | 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 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 C31-630-KMB model number is decoded
SKF lists C 31/630 KMB in the dimension series 31 CARB toroidal roller bearings: the toroidal roller profile both follows tolerates angular misalignment and lets the inner ring slide axially inside the outer ring, giving free axial displacement at the non-locating position. Reading the code: C marks the CARB toroidal family, the first two digits (31) identify the ISO dimension series and the last two (630 mm (slash-size)) encode the 630 mm bore; suffixes describe bore and execution. 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 630 mm seat. Selection arithmetic: C 11800 kN against C0 20800 kN gives a C0/C ratio of 1.76, and the 1290 kN fatigue load limit Pu sets the contamination-adjusted life floor. Open executions accept relubrication — route it through the outer-ring groove on sizes that have one and purge stale grease at service intervals. Grease through the annular groove features where provided; on open executions feed lubricant past the long roller set at assembly, since the 315 mm wide cavity does not fill itself.
Typical equipment & failure modes
Common applications
- heavy industrial gearbox layshafts used as the non-locating position
- winder and reel drums in paper and steel strip plants
- paper machine drying cylinders and calender rolls with long, thermally expanding shafts
- continuous-caster guide rolls and slab-caster segments under heat growth
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
- 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
- grease churning and overheating when a high-speed thrust position is over-packed
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.
- Envelope-identical spherical roller bearings (same ISO 15 d×D×B) are not drop-in equivalents — they locate the shaft axially, while C 31/630 KMB must float; the two are designed to be used as a pair.
- Never use C 31/630 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.
- 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 KMB); VE240 vibrating-screen variants and sealed 2CS/2NS variants have their own figures even at the same envelope.
- 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 KMB mean in SKF part numbering?
C marks CARB; 31 the dimension series; the size code gives 630 mm bore; KMB is the execution (tapered 1:12 bore for adapter (H) sleeve mounting, 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 KMB 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 KMB 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.