Type N, NU Bearings of type N have two integral flanges on inner ring and a flangeless outer ring. This type of bearings permits axial displacement in double directions of the housing relative to the shaft. The bearings of type NU have two integral flanges on outer ring and a flangeless inner ring. This type of bearings permits axial displacement in double directions of the housing relative to the shaft. Type NJ, NF Bearings of type NJ have two integral flanges one on the outer ring, and one on the inner ring. This type of bearing can carry a certain amount of axial load in a single direction. Bearings of type NF have one flange on the outer ring, and two integral flanges on the inner ring. This type of bearing can carry a certain amount of axial load in a single direction.
Minimum Load-cylindrical Roller Bearings
In order to keep bearings working in good condition, a minimum load must be imposed on bearings, particularly on bearings working at high speeds, high accelerations, or with the load direction changing frequently, because under these working conditions, inertial force of balls and cage and lubricant friction will have bad influence on the rotation of bearings, and detrimental sliding movement may be caused.
Minimum Load-cylindrical Roller Bearings
In order to keep bearings working in good condition, a minimum load must be imposed on bearings, particularly on bearings working at high speeds, high accelerations, or with the load direction changing frequently, because under these working conditions, inertial force of balls and cage and lubricant friction will have bad influence on the rotation of bearings, and detrimental sliding movement may be caused.
Where
n - Working speed, r/min
nr -(0.8～0.9)Limiting speed, r/min
dm - Mean bearing diameter dm=0.5(d+D), ,mm
Kr - Minimal load factors,the values are
When bearings are started at low ambient temperatures or in the condition that the viscosity of the lubricant is very high, bigger minimum load is required. Usually, the weight of the bearing supporting parts plus the load on the bearing have been over the required minimum load. If the weight cannot be up to the minimum load, extra radial load must be exerted on this type of bearing in order to meet the requirement of minimum load.
When bearings are started at low ambient temperatures or in the condition that the viscosity of the lubricant is very high, bigger minimum load is required. Usually, the weight of the bearing supporting parts plus the load on the bearing have been over the required minimum load. If the weight cannot be up to the minimum load, extra radial load must be exerted on this type of bearing in order to meet the requirement of minimum load.
US 9768 
GB 7324 
CA 6251 
AU 5750 
IE 3886 
NZ 2411 
SG 1009 
BR 539 
