The dynamic load rating of 40.8 kN characterises this bearing. The static load rating is 24 kN. The limiting speed is 7500 rpm. The closed side wards off, the open side supplies — which is why the shield belongs towards the surroundings and the free rolling chamber towards the lubricant reservoir of the assembly. The single shield turns an otherwise symmetrical bearing into a directional component, and most of what has to be observed with this version follows from that.
On the closed side a sheet-metal part fixed in the outer ring reaches close to a shoulder of the inner ring without touching it; the remaining gap holds back coarse contamination and in doing so generates neither a frictional torque nor a heat source. On the open side the rolling chamber remains accessible: lubricant from the surrounding space can reach the rolling contact, frictional heat can be carried away with it, and relubrication through the assembly is possible in principle — properties that a doubly closed version does not offer.
The mounting direction is thereby part of the design and not left to the assembly floor: the shield faces the loaded surroundings, the open side faces the clean interior supplied with lubricant. Two further points hang on the same asymmetry. First, the grease charge is held back on one side only, so with a vertical shaft, high speed or heavy vibration it has to be checked whether the lubricant remains in the rolling chamber.
Second, the gap is no barrier against liquid or fine dust, so for wet surroundings a contact version or an upstream seal is to be provided. Normal radial clearance is matched to one interference-fitted ring and a moderate temperature difference; because the shield does not touch the rings, it exerts no influence on the clearance itself. Through-hardened standard bearing steel sets the temperature and load frame of the rings.
ManufacturerNKE
Bearing typeDeep-groove ball bearings
Bore d40 mm
Outer Ø D90 mm
Width B23 mm
Dyn. load C40.8 kN
Stat. load C₀24 kN
Fatigue limit Pu1.1 kN
Limiting speed7,500 min⁻¹
Weight0.63 kg
Sealsshield on one side
Clearancenormal radial internal clearance
Cagepressed steel cage
Materialstandard bearing steel
Tolerancetolerance class P0/PN (ABEC 1)
Shaft shoulder dₐ49–56.1 mm
Housing shoulder Dₐ73.8–81 mm
Bore typecylindrical bore
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NKE 6308-Z Kugellager (40x90x23)
— 40 x 90 x 23 mm
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Same dimensions means the same bearing type and matching main dimensions (d × D × B). Sealing, cage, internal clearance and execution (e.g. material, precision, grease fill) are encoded in the suffix and may differ — please check before ordering. Equivalent additionally means the same sealing, internal clearance and tolerance class; the cage and other suffix features (e.g. lubrication groove) may differ.
