Double row cylindrical roller bearings
Double row cylindrical roller bearings have a low cross section, high load carrying capacity and high stiffness. Therefore they are mainly used in machine tools, rolling mill stands, plastic calenders, grinding mills and also large gearboxes.
SKF produces double row cylindrical roller bearings mainly in the NNU design (fig 1) and the NN design (fig 2). The bearings are separable, i.e. the ring with integral flanges together with the roller and cage assemblies can be mounted separately from the other bearing ring or all bearing components can be mounted separately. This facilitates the mounting, inspection and maintenance of these bearings.
Double row cylindrical roller bearings are produced with both cylindrical bore and tapered bore; bearings of the NN design are generally supplied with tapered bore. When mounting bearings with tapered bore it is possible to achieve a certain radial internal clearance or a given preload.
The bearings, except those of the NNUP design (fig 3) allow axial displacements between shaft and housing to take place inside the bearing itself within certain limits.