The rollers of NN design cylindrical roller bearings are guided between integral flanges on the
inner ring, while the rollers of NNU design bearings are guided between integral flanges on the outer ring. In either case, the other ring has no flanges. Therefore, the bearing can accommodate axial displacement of the shaft relative to the housing in both directions, within the bearing.
These bearings are separable, i.e. the
bearing ring with integral flanges, together with the
roller and cage assembly can be separated from the flangeless ring, to facilitate mounting and dismounting.
NN design bearings can provide a unique balance between load carrying capacity, rigidity and speed and are therefore typically used as the drive end bearing in machine tool spindles. Boundary dimensions of NN design bearings are in accordance with ISO Dimension Series 30 (NN 30 series designation).
NNU design bearings, with a very low cross sectional height, provide a higher degree of stiffness than bearings in the NN 30 series. However, NN 30 series bearings can accommodate heavier loads. Boundary dimensions of NNU design bearings are in accordance with ISO Dimension Series 49 (NNU 49 series designation).
Double rows cylindrical roller bearings for machine tool