As an alternative to needle roller bearings, high-precision cylindrical roller bearings NNU49 and NN30 also fulfil the high requirements of printing machines in terms of rigidity and precision.
These are double-row bearings. Depending on the design, the rolling elements are guided via ribs on the inner ring (series NN30) or on the outer ring (NNU49). The cage is usually made of brass, but can also be supplied in steel or plastic if required. The inner ring has a tapered bore so that the radial internal clearance can be adjusted easily. This means it is possible to adjust the internal clearance with precise measuring devices at a precision of +/- 1µm. In many cases the bearing is operated with preload (negative internal clearance) in order to increase rigidity.