Double row cylindrical roller bearings
SKF super-precision double row cylindrical roller bearings are manufactured as standard in the NN 30 (fig. 1) and NNU 49 (fig. 2) series.
Both series are available with either a cylindrical or a 1:12 tapered bore (designation suffix K). In machine tool applications, cylindrical roller bearings with a tapered bore are preferred over bearings with a cylindrical bore, because the taper enables more accurate adjustment of clearance or preload during mounting.
NN 30 seriesBearings in the NN 30 series can provide a unique balance between load carrying capacity, rigidity and speed. They are therefore typically used as the non-tool end bearing in machine tool spindles.
NN 30 series bearings have three integral flanges on the inner ring and no flanges on the outer ring.
NNU 49 seriesBearings in the NNU 49 series, with a very low cross-sectional height, provide a higher degree of stiffness than bearings in the NN 30 series, but a somewhat lower load carrying capacity.
NNU 49 series bearings have three integral flanges on the outer ring and no flanges on the inner ring.