NSK NU208 EMC3 Zylinderrollenlager (40x80x18)

As a cylindrical roller bearing, this bearing carries high radial loads with limited axial capacity. For this NSK bearing, 40x80x18 mm and a weight of 0.435 kg apply; the specification table holds the further technical particulars. This variant features increased radial clearance (C3). This open version is intended for bearing positions at which a normal radial clearance would fall as far as a preload of the roller contact once mounted and at temperature.

In this design, radial clearance is directly a design parameter and not merely a manufacturing dimension: it fixes how many rollers carry load at the same time. If the operating play comes out too small, the load zone extends beyond half the circumference, the unloaded rollers are pressed against the raceway, friction and heat generation rise, and the heat introduced reduces the play further.

If, conversely, too much play remains, only a narrow zone carries, and the most heavily loaded roller takes a larger share of the radial force than a calculation assuming even distribution would suggest. The increased clearance (C3) shifts the initial play upward far enough that the usual consumers — the interference fit of the inner ring on the shaft and a temperature difference between the rings — still leave a residual play within the intended range in service.

The interference fit is no special case here: because the inner ring and the outer ring assembly are fitted separately, the inner ring is routinely set tight on the shaft under rotating point load, and a tight seat expands the ring before the arrangement even goes into service. Every heat source on the shaft side acts in the same way, from the gear teeth to a flange-mounted drive.

For the specific bearing position, the choice of fits, the temperature gradient to be expected between inner and outer ring, and the magnitude and direction of the radial force should therefore be assessed together. The increased clearance changes nothing about the rest of the layout: axial guidance still follows from the rib arrangement, and the open form presupposes sealing by the surrounding construction.