C3068-KM bearing: complete specifications & equivalents
The C3068-KM is a ISO 15 radial bearing sized 340 x 520 x 133 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 340 mm |
| Outer diameter D | 520 mm |
| Width B | 133 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 2900 kN |
| Basic static load rating C0 | 5000 kN |
| Fatigue load limit Pu | 375 kN |
| Reference speed (thermal) | 950 rpm |
| Limiting speed (mechanical) | 1300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 100000 g |
| Manufacturer designation | C 3068 KM |
| 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 | 13.386 in |
|---|---|
| Outer diameter D | 20.472 in |
| Width B | 5.236 in |
| ISO bore code | 68 |
| Radial section height (D−d)/2 | 90 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) | 13 of 33 |
| Bore above smallest C3000-series size | 220 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| C3068-M | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 340×520×133 mm ISO 15 envelope and equivalent catalogue C/C0; C 3068 M is the cylindrical-bore M 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 C3068-KM model number is decoded
C 3068 KM is the dimension series 30 CARB toroidal roller bearings member of the CARB range: 340 mm bore, 520 mm OD, 133 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 (30) identify the ISO dimension series and the last two (68) encode the 340 mm bore; suffixes describe bore and execution. The open execution relies on the housing seals and lubrication system, fed through groove/hole features on the large sizes. Explorer-class heat treatment and the crowned roller profile keep edge stress down when the 340 mm shaft deflects; the 950 r/min reference and 1,300 r/min limiting speed are both catalogue values. Selection arithmetic: C 2900 kN against C0 5000 kN gives a C0/C ratio of 1.72, and the 375 kN fatigue load limit Pu sets the contamination-adjusted life floor. Mounting: mount on the adapter (H) sleeve matched to the 1:12 tapered bore, drive up to the catalogue reduction and lock the nut; never press through the 133 mm roller set, and leave the free-end housing shoulder clear so axial float is unrestricted.
Typical equipment & failure modes
Common applications
- 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
- vibrating screen exciters fitted with the VE240 tolerance execution
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
- brass cage pocket wear under marginal lubrication in the large-bore M/MB executions
- rolling-contact fatigue spalling after the catalogue L10 life is exhausted
- grease churning and overheating when a high-speed thrust position is over-packed
Selection pitfalls — read before you substitute
- Above 200 mm bore these bearings weigh tens of kilograms (100 kg here) — lifting gear and induction heating are mandatory, and a cocked ring scores the toroidal raceway before start-up.
- Tapered-bore K executions mount on adapter sleeves (1:12) and K30 on withdrawal sleeves (1:30) — the 340 mm bore changes the sleeve family, and the drive-up procedure differs accordingly.
- Reference and limiting speeds are different limits: the 950 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.
- Never use C 3068 KM 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 quoted 2900/5000 kN ratings belong to this exact execution (C 3068 KM); VE240 vibrating-screen variants and sealed 2CS/2NS variants have their own figures even at the same envelope.
- The 2900/5000 kN ratings and 100000 g mass are SKF catalogue values transcribed from ch. 10.1 of PUB BU/P1 17000 (PDF table page 864); 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
Is the C 3068 KM 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.
Which dimensions does the C 3068 KM have?
A C 3068 KM measures 340 mm bore × 520 mm outside diameter × 133 mm width (13.386 × 20.472 × 5.236 in). From SKF catalogue PUB BU/P1 17000: dynamic C 2900 kN, static C0 5000 kN, fatigue limit Pu 375 kN, reference speed 950 r/min, limiting speed 1,300 r/min, mass about 100000 g.
What does C 3068 KM mean in SKF part numbering?
C marks CARB; 30 the dimension series; the size code gives 340 mm bore; KM is the execution (tapered 1:12 bore for adapter (H) sleeve mounting, machined brass M cage). The envelope follows ISO 15 and matches spherical roller bearing outlines, but the functions differ.
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.