FAG 6208-C-HRS-C3 (-RSR-C3) Kugellager (40x80x18)

This FAG bearing measures 40x80x18 mm and weighs 0.37 kg; the specification table carries the supplementary technical details. This variant features a contact seal and increased radial clearance (C3). Increased clearance (C3) and a contact seal on one side belong at positions that run warm and at the same time have to be shielded against a loaded side.

In this combination sealing and clearance class are linked through temperature, but not in the same way as in a doubly closed version. The contact seal on one side lays an elastomeric lip against the inner ring and keeps moisture and fine dust out of the rolling chamber; in doing so it produces a load-independent frictional torque whose heat arises directly at the inner ring and thus warms the very ring whose expansion closes the clearance.

The open opposite side counteracts this warming, because lubricant from the surrounding space can reach the rolling contact and carry frictional heat away with it; how large that contribution turns out depends on the assembly and not on the bearing alone. Increased clearance (C3) holds an allowance ready for the remaining sum of interference fit, seal friction and external heat flow, so that a residual clearance establishes itself in the warm running state at which the rolling contact is not preloaded.

If it is set too small, frictional torque and temperature rise further and reduce the remaining clearance additionally; if it is set too wide, the load zone narrows and, at low radial load, the load-free part of the ball set can slide. The asymmetry also implies a mounting instruction: the seal faces the loaded side, the open side the interior supplied with lubricant, and this assignment is to be recorded because it is not recognisable during assembly.

The permissible speed follows from the contact version and not from the clearance class. Through-hardened standard bearing steel sets the frame for hardness and dimensional accuracy of the rings; the temperature limit of the sealing material is to be taken separately from the designation. Contact seal on one side (rubber lip seal) — Dimensional/form-fit equivalent — verify suffix-level details for critical applications. Matching suffixes are also listed by SKF (RSH, RS1), NSK (DU), NTN (LU) and NACHI (NSE).