Double row cylindrical roller bearings are divided into bearings with cylindrical bore and tapered bore (add K behind bearing type). This type of roller bearings have compact structure, good rigidity, heavy load carrying capacity, and little distortion under loads. Because of their second row of rollers, double row cylindrical roller bearings are suitable for heavy radial loads. Double row cylindrical roller bearings are applicable for the machine tool spindle. Tapered inner bore could fine adjust clearance, simplify positioning fixture and be convenient to mount and dismount.
Depending on the existence of ribs on their rings, double row cylindrical roller bearings are classified into NN, NNU types.
Type NN double row cylindrical roller bearings have two integral flanges on the inner ring, a flangeless outer ring and a center flange in the middle. Double-row cylindrical roller bearings permit axial displacement in double directions of the housing relative to the shaft.
Type NNU double row cylindrical roller bearings have two integral flanges on the outer ring, a non-contacting inner ring and a center flange in the middle. Double row cylindrical roller bearings permit axial displacement in double directions of the housing relative to the shaft. Therefore, this type of bearing is suitable to be used as non-locating bearings.
