Cylindrical roller Bearings
Most of cylindrical roller bearings are separable which make it very convenient to mount and dismount. Cylindrical roller bearings can carry heavier radial load and are suitable to be used in the condition of high speed.
This type of bearings only can allow a small angular error between inner axes and outer axes in the range of 2 - 4. Therefore it requires higher machined precision on shaft and housing; otherwise asymmetrical load and stress would be focused at the position of raceway. However this situation can be improved by correcting the contacted generatrix of rollers or raceways.
According to different rows cylindrical roller bearings are divided into single row double-row and multi-row cylindrical rollers. These differences are also displayed on the design of flange position. The common used types of cylindrical roller bearings are as following.
Single-Row Cylindrical Roller Bearings
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.
Therefore this type of bearings is suitable to be used as non-locating bearings.
Type NJ NF
Bearings of type NJ have two integral flanges on outer ring and one on inner ring. This type of bearings can carry a certain amount of axial loads in single direction.
Bearings of type NF have one flange on outer ring and two integral flanges on inner ring. This type of bearings can carry a certain amount of axial loads in single direction.
Therefore they are suitable to be used as an axial location bearing in single direction.
Type NUP NFP
Bearings of type NUP have two integral flanges on outer ring one flange and separable loose flange on inner ring. This type of bearing can carry a certain amount of axial loads in double directions.
Bearings of type NFP have one flange a loose flange on outer ring and two integral flanges on inner ring. This type of bearing also can carry a certain amount of axial loads in double directions.
This type of bearings can limit the displacement in double directions of the housing relative to the shaft.
Therefore they are suitable to be used as an locating bearing.
Type NH (NJ+HJ)
Bearings of type NH are combined by the bearing of type NJ and the bearing of type HJ with catercornered flange. Comparing to NUP type with short flange ring and non-locating loose flange Type NH can take the advantage of the whole inner ring width of NJ to match with axes tightly. Moreover its quite convenient to mount and dismount.
This type of bearing can limit axial displacement in double directions of the housing relative to the shaft. Therefore they are suitable to be used as a locating bearing.
Double-Row Cylindrical Roller Bearings
Double-row cylindrical roller bearings are divided into bearings with cylindrical inner bore and tapered inner bore (added K behind bearing type). This type of bearing has these advantages such as compact structure good rigidity heavy load carrying capacity and little distortion under loads. Consequently its applicable for the machine tool spindle. Tapered inner bore could fine adjust clearance simplify positioning fixture and be convenient to mount and dismount.
Type NN NNU
Bearings of type NN have two integral flanges on inner ring a flangeless outer ring and a centre flange in the middle. This type of bearings permits axial displacement in double directions of the housing relative to the shaft.
Bearings of type NNU have two integral flanges on outer ring a non-contacting inner ring and a centre flange in the middle. This type of bearings permits axial displacement in double directions of the housing relative to the shaft.
Therefore this type of bearings is suitable to be used as non-locating bearings.
Type NNF
Bearings of type NNF are one kind of double-row cylindrical roller bearings full of rollers which is consist of outer ring with a center flange two inner rings with double flanges. Rollers are guided by flanges on inner ring and two inner rings are fixed up by fastening ring. This structure can carry not only a lot of heavy radial load and axial load but also tilting moment. Therefore they are suitable to be used as non-locating bearings.
Bearings of type NNF have contact seals at two sides. And it is filled in grease lubricant. The working temperature would be -50 Celsius degree to +110 Celsius degree.However after considering of seal material available working temperature shall be -40Celsius degree to +80 Celsius degree. Under appropriate conditions sealed NNF bearing need little maintenance and could be kept long time in water vapor or polluted environment. When mid or high speeding bearing can got make-up lubricating through lubrication groove and bore.
Four-Row Cylindrical Roller Bearings
four-row cylindrical roller bearings are mainly used for rolling mill like cold hot rolling mill and blooming mill. The bearing is separable i.e. The rings and rolling elements could be separated. Therefore it is convenient to wash check mount and dismount.
Type FC
The bearings of type FC are consisted of two outer rings and one inner ring which have two integral flanges on outer rings a center flange in the middle and a flangeless inner ring.
Type FCD
Essentially type FCD bearing is consisted of two type NN bearings.
Type FC and FCD bearing can permit axial displacement in double directions of the housing relative to the shaft
Therefore they are suitable to be used as non-locating bearings. Normally their cages is made by solid machined cage.
Cages
Most cages for single row cylindrical roller bearings are pressed steel cages or machined brass cages. According to different working conditions and customers requirements cages with other design and structure could be supplied.
Full Complement Cylindrical Roller Bearings (Full Complement Bearings) are designed to carry heavy load. Comparing with traditional bearings with cage, full complement cylindrical bearings have much higher loading capacity. The radial cross section of the type of bearings is very small. So it can be very space – saving. However the limiting speed of the bearings is relatively lower. All the multi – row cylindrical roller bearings are with a lubrication groove and one nipple on the outer ring.
A minimal load is required (C/P <25) for the bearings to run well in succession. Otherwise wear may happen when lubrication is running out or rotating speed is high.
NCF•••V type Full Complement Cylindrical Roller Bearings are with a single rib on one side of the outer ring. A snap ring is on the other side which makes the shaft be stationary in single direction. The axial gap “s” inside the bearings ensures the axial displacement of shaft to the bearing housing case. For this “s” value, please consult technical service.
NJ•••V type Full Complement Cylindrical Roller Bearings is applied under very high loads and slow rotating speed conditions. The rollers are self – locked and will not fall apart even if the inner ring is removed. Therefore, the mounting and dismantling of the type of bearings are convenient. The bearings can carry axial load in one direction.
NNF•••2LSNVY type double – row Full Complement Cylindrical Roller Bearings are with two inseparable inner rings joined by a holding ring. There is a rib in middle of the outer ring. The bearings can carry axial load in both directions and be used ad stationary bearings. As the distance between the two rows of rollers is big, the bearings can also take some overturning moment. On the outer ring there are two snap grooves for axial orientation. This type of bearings is with contact seals on both sides and with lithium based grease. The operation temperature limit for the bearings is from -40 to 80℃. The kind of bearing is generally free of maintenance under some certain conditions. But in case that there is vapor or dust, and the bearings are running in medium or high speed, supplement lubricant is absolutely necessary. If using rare oil as lubricant, the seals should be removed and all the grease with the bearings be washed out. In that case, the limit rotating speed can be increased 30%.
The dimension tolerance and geometry deviation of the type of bearings are in accordance with Grade P0 of GB 307.1--1994(ISO492-1994). And the normal radial clearance is with group C0. Bearings with normal radial clearance of Group C2 or C4 are also available. In that case some suffix should be added to the bearing code. For example, bearing with group C3 are generally selected for the plastic extruders.
If you have requirement for higher grade bearings, please contact service.
For mounting tolerance, you can refer to the selection principle of housing tolerance and shaft tolerance limits. Some certain axial loads are allowed for the type of bearings. In that case, sufficient lubrication is a premise. In the single direction stationary bearings and stationary bearings, the rib that carrying axial load must be fully supported.
