This SKF bearing measures 40x90x23 mm and weighs 0.635 kg; the specification table carries the supplementary technical details. This variant features increased radial clearance (C3). The shields do not touch the rings and therefore exert no influence on the clearance; what they change is the path by which heat leaves the bearing. The combination of shields on both sides with increased clearance (C3) describes a position that is closed and nevertheless runs warm.
Because no lubricant is routed through the rolling chamber, the frictional heat leaves the bearing through the inner and outer ring, and the ring with the better thermal connection — as a rule the outer ring in the housing — stays cooler than the inner ring on the shaft. It is precisely this difference that consumes clearance: the warmer inner ring expands further and, together with the share the interference fit has already taken, the remaining clearance can fall below the intended range.
Increased clearance (C3) holds an allowance ready for that, so that a residual clearance establishes itself in the warm running state at which the rolling contact is not preloaded. The second effect of the same temperature concerns the lubricant: the grease charge is enclosed by the shields and dimensioned for the service life, so that its ageing at elevated temperature — rather than material fatigue — frequently becomes the limiting quantity.
The operating temperature of the position is therefore to be checked against the data for the grease charge; where it lies above, a version with a different filling or a relubricatable solution is to be selected rather than adjusting the clearance class alone. Since the shields do not touch the rings, they contribute neither a frictional torque nor a heat source of their own; the permissible speed follows from the cage and the lubricant.
Through-hardened standard bearing steel sets the frame for hardness and dimensional accuracy within which this interplay holds. Metal shields on both sides — Dimensional/form-fit equivalent — verify suffix-level details for critical applications. Matching suffixes are also listed by FAG (2Z), NSK (ZZ), NTN (ZZ) and NACHI (ZZE).
ManufacturerSKF
Bearing typeDeep-groove ball bearings
Bore d40 mm
Outer Ø D90 mm
Width B23 mm
Weight0.635 kg
Sealsshields on both sides
Clearanceradial internal clearance greater than normal
Cagepressed steel cage
Materialstandard bearing steel
Tolerancetolerance class P0/PN (ABEC 1)
Bore typecylindrical bore
€61.90/ pc
incl. VAT, plus shipping · price drops with quantity
In stock
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QtyUnit priceDisc.
1 – 4€61.90—
5 – 9€60.05−3 %
10 – 24€58.81−5 %
25 – 49€56.95−8 %
50 – 99€55.71−10 %
4 more for −3% volume discount
From 100 pcs: price and lead time on request – subject to review.
Total (1 pc)€61.90
SKF 6308-2Z/C3HT 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.
