C30-850-KMB bearing: complete specifications & equivalents
The C30-850-KMB is a ISO 15 radial bearing sized 850 x 1220 x 272 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 850 mm |
| Outer diameter D | 1220 mm |
| Width B | 272 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 11600 kN |
| Basic static load rating C0 | 24500 kN |
| Fatigue load limit Pu | 1430 kN |
| Reference speed (thermal) | 320 rpm |
| Limiting speed (mechanical) | 450 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1110000 g |
| Manufacturer designation | C 30/850 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 & C3000-series range
| Bore d | 33.465 in |
|---|---|
| Outer diameter D | 48.031 in |
| Width B | 10.709 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 185 mm |
| Smallest bore in C3000-series | 120 mm |
| Largest outer diameter in C3000-series | 1420 mm |
| Width range across C3000-series | 46–308 mm |
| Bore position in C3000-series (smallest first) | 30 of 33 |
| Bore above smallest C3000-series size | 730 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| C30-850-MB | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 850×1220×272 mm ISO 15 envelope and equivalent catalogue C/C0; C 30/850 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 C30-850-KMB model number is decoded
C 30/850 KMB belongs to the CARB family — compact aligning roller bearings: envelope 850×1220×272 mm, radial rating 11600/24500 kN C/C0, and no axial-locating function by design. Reading the code: C marks the CARB toroidal family, the first two digits (30) identify the ISO dimension series and the last two (850 mm (slash-size)) encode the 850 mm bore; suffixes describe bore and execution. The KMB suffix is a machined two-piece brass cage guided on the inner ring, the standard choice for wide, large-bore CARB sizes where a polymer cage would run beyond its temperature or load limit. Pairing rule: use the CARB bearing opposite one locating spherical or tapered bearing — never at both shaft ends — and check the locating bearing takes 100 % of the thrust, since C 30/850 KMB deliberately carries none. 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 272 mm wide cavity does not fill itself.
Typical equipment & failure modes
Common applications
- 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
- winder and reel drums in paper and steel strip plants
Known failure patterns
- roller-end and flange smearing after lubricant starvation at the long roller contacts
- thermal preloading when a shaft is located at both ends and growth has nowhere to go
- 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
- oil starvation at the sliding contact zones of large spherical roller thrust bearings on forced-feed trips
Selection pitfalls — read before you substitute
- At 850 mm bore the 1110 kg mass and 272 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 850 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.
- 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 30/850 KMB must float; the two are designed to be used as a pair.
- The 11600/24500 kN ratings and 1110000 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
What does C 30/850 KMB mean in SKF part numbering?
C marks CARB; 30 the dimension series; the size code gives 850 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 30/850 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 30/850 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.