Double row cylindrical roller bearing has cylindrical internal hole and conical internal hole (bearing postcode plus K) for two structures. This kind of bearing has the advantages of compact structure, big rigidity, big bearing capacity, small deformation after bearing load and so on. Conical bore can also play the role of minor adjustment clearance and can simplify the positioning device structure, which is easy to install and disassemble. The commonly used double row cylindrical roller bearings have the following forms.

NN, NNU type

The outer ring of NN bearing has no baffle, and the inner ring has baffle on both sides and middle baffle. The axial displacement of the shaft relative to the bearing seat may be allowed in both directions.

The outer ring of the NNU bearing has two baffles and the middle baffle on both sides, and the inner ring has no baffle. The axial displacement of the shaft relative to the bearing seat may be allowed in both directions. Therefore, this kind of structure is suitable for floating end bearing.

NNF type

The NNF type bearing is a double row full cylindrical roller bearing, which consists of an outer ring with middle baffle and two inner rings with double baffle. The roller is guided by the baffle of the inner ring, and the two inner rings are held together by fasteners. In addition to the large radial and axial loads, the structure can also withstand the overturning torque, so it is commonly used as a fixed end bearing.

NNF bearings are provided with contact seals on both sides. Bearing inner filled with grease. The working temperature of the grease is for - 50 ℃ to + 110 ℃. Due to the limitation of sealing material, the working temperature of bearing is limited to  40 ℃ to + 80 ℃. The NNF bearing with seal does not need to be maintained under good working conditions. If the bearing is kept in water vapor or polluted environment for a long time and it is operated at medium or high speed, it can be lubricated by lubricating oil groove and lubricating oil hole on the outer ring.