NACHI 6008 ZECM Kugellager (40x68x15)

At 40x68x15 mm and a unit weight of 0.18 kg, the installation envelope is fixed; further technical details are held in the specification table. The shield exerts no influence on the clearance — it does not touch the rings — so the narrowed tolerance arrives directly in the mounted state here. In this version a directional component and a more narrowly defined clearance meet, and in series production both features have to be managed.

The single shield consists of a sheet-metal part fixed in the outer ring that reaches close to a shoulder of the inner ring without touching it: the closed side holds back coarse ingress, the open side lets lubricant from the surrounding space reach the rolling contact and frictional heat leave with it. Because this bearing thereby has two different sides, its mounting direction belongs in the assembly documents; a reversed position inverts the direction of protection without this being noticeable during assembly.

Normal radial clearance with narrowed tolerances does not shift the clearance range but reduces the permitted scatter within the normal class, so that two bearings of the same designation lie closer together in the mounted state. That takes effect precisely where the residual clearance is not set on the individual unit but is fixed by fits and manufactured dimensions — on radial stiffness, vibration behaviour and the size of the load zone.

One advantage of this combination is that the non-contacting shield contributes neither a frictional torque nor a heat source and does not influence the clearance, so the narrower distribution arrives undamped in the running behaviour. The choice of class itself is not replaced by it: interference fit and temperature gradient still consume the same share as under the undivided normal clearance.

Through-hardened standard bearing steel supplies the hardness and dimensional accuracy on which a narrow distribution rests; sealing against liquid and fine dust remains the task of the surrounding design.