Needle roller bearings consist of many thin and long needle roller whose diameter is from three to ten longer than their diameters with compact structure.The inner diameter of the needle roller draw near the outer diameter of the bearing,so they will have the large radial load capacity.
一. The main form of structure
1 . Solid outer ring needle roller bearings NA,0000,NKI
This kind bearing have inner and outer rings(lock ring,needle roller,and cage).The limited rotating speed is higher.There are two kinds needle roller bearings according the rows of bearing,single and double rows.
Single : NA48,NA49,NA69(<32mm) and NKI
There are double lock ring of needle roller bearings whose diameter is shorter than 7mm,and there are double ribs of these needle roller bearings whose diameter is longer than 7mm.
Double : NA69 series (d≥32mm)
2 . The 0000 series of the needle roller and cage assembly K
The needle roller and cage assembly are separate,and the needle roller bearing is conducted precisely by cage.This kind of bearings are without rings,with small radial surface and heavy carrying capacity,so they are applicable to restricted support structure on radial mounting dimensions.Matching the shaft surface with the bearing and the surface of the housing hole directly regard as the bearing rolling surface of inside and outside.The hardness of surface is generally 58~64 HRC. The deep of the Surface hardened layer is almost 0.6~1mm,roughness of roller surface is generally 0.32μm.when the precise of Rotation of the shaft is required, roughness is 0.2μm.
3 . The series of HK and BK (without inner ring but with stamping outer ring with a cage)
HK series : Both ends of the bearing are perforated
Bk series : One end of the bearing is a sealed type.
There is no the support in extended end ,and they can withstand small axial travel power,and closed end is with the function of sealing.
This kind of needle roller bearing is consists of thin-walled punching outer ring,cage and roller.Their cost is cheap and capacity is very high.And they are suitable for restricted support structure on radial mounting dimensions.The shaft diameter surface that matches the bearing is hardened directly as a raceway.The bearing is fitted with an interference fit into the seat hole without the need for axial positioning.Bearings should be filled with enough grease before installation. Normally, no further lubrication is required after assembly.
二. The material of cage
Needle roller bearings are generally made of high-quality low-carbon steel, can also be used to inject nylon and other materials
三, The allowed tilt angle
Needle roller bearings are generally not allowed to tilt the angle. During the process of using, the maximum angle in the full length of the needle can not be greater than 0.25％~0.3％ of the angle.
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