For this SKF bearing, 40x90x23 mm and a weight of 0.63 kg apply; the specification table holds the further technical particulars. This variant features a contact seal and increased radial clearance (C3). Here the seal choice and the clearance class hang together: sealing on both sides by contact introduces a load-independent frictional torque, and increased clearance (C3) holds the corresponding share in reserve.
In a version sealed by contact on both sides an elastomeric lip bears against the inner ring and keeps moisture and fine dust away from the rolling chamber. The price for this is a frictional torque that is present independently of the load — and that torque becomes visible not only as lost power but first of all as heat at the place where it arises: at the contact face between lip and inner ring.
As a result the temperature difference that closes the clearance arises partly inside the bearing itself and not exclusively through an external heat source. To this share is added the interference fit on the shaft, which expands the inner ring, and in many applications the ambient heat of the drive as well. Increased clearance (C3) holds an allowance ready for this sum so that a residual clearance establishes itself in the warm running state at which the rolling contact does not run under constraint; if it turns out too small, the frictional torque rises further and the additional heat reduces the remaining clearance further still.
The grease charge is enclosed by the seals and dimensioned for the service life, which is why its ageing at the elevated operating temperature has to be assessed as well — it, rather than material fatigue, frequently limits the life at moderate load. In this version the permissible speed follows from the seal and not from the clearance class: a wider clearance does not raise the limit that the contact version sets.
Through-hardened standard bearing steel determines the temperature and load frame of the rings; the temperature limit of the sealing material is to be taken separately from the designation. Contact seals on both sides (rubber lip seal) — Dimensional/form-fit equivalent — verify suffix-level details for critical applications. Matching suffixes are also listed by FAG (2RSR), NSK (DDU), NTN (LLU) and NACHI (2NSE).
ManufacturerSKF
Bearing typeDeep-groove ball bearings
Bore d40 mm
Outer Ø D90 mm
Width B23 mm
Weight0.63 kg
Sealscontact seals on both sides
Clearanceradial internal clearance greater than normal
Cagepressed steel cage
Materialstandard bearing steel
Tolerancetolerance class P0/PN (ABEC 1)
Bore typecylindrical bore
€30.40/ pc€60.76−50 %
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QtyUnit priceDisc.
1 – 4€30.40—
5 – 9€29.50−3 %
10 – 24€28.89−5 %
25 – 49€27.98−8 %
50 – 99€27.37−10 %
4 more for −3% volume discount
From 100 pcs: price and lead time on request – subject to review.
Total (1 pc)€30.40
SKF 6308-2RS1/C3WT 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.
