Cylindrical roller bearings consist of an inner and outer ring, a roller-retaining cage, and a complement of controlledcontour cylindrical rollers. Depending on the type of bearing, either the inner or the outer ring has two roller-guiding ribs. The other ring is separable from the assembly and has one rib or none. The ring with two ribs axially locates the position of the roller assembly. The ground diameters of these ribs may be used to support the roller cage. One of the ribs may be used to carry light thrust loads when an opposing rib is provided.The decision as to which ring should be double ribbed is normally
determined by considering assembly and mounting procedures in the application.
Type NU has double-ribbed outer and straight inner rings. Type Nhas double-ribbed inner and straight outer rings. The use of either type at one position on a shaft is ideal for accommodating shaft expansion or contraction. The relative axial displacement of one ring to the other occurs with minimum friction while the bearing is rotating. These bearings may be used in two positions for shaft support if other means of axial location are provided. Type NJ has double-ribbed outer and single-ribbed inner rings. Type NF has double-ribbed inner and single-ribbed outer rings. Both types can support heavy radial loads, as well as light unidirectional thrust loads. The thrust load is transmitted between the diagonally opposed rib faces in a sliding action.
When limiting thrust conditions are approached, lubrication can become critical. Your Timken When thrust loads are very light, these bearings may be used in an opposed mounting to locate
the shaft. In such cases, shaft endplay should be adjusted at time of assembly.
Type NUP has double-ribbed outer and single-ribbed inner ring with a loose rib that allows the bearing to provide axial location in both directions. Type NP has a double-ribbed inner ring and
a single-ribbed outer ring with a loose rib. Both types can carry heavy radial loads and light thrust loads in both directions. Factors governing the thrust capacity are the same as for types NJ and
NF bearings.A type NUP or NP bearing may be used in conjunction with type N or NU bearings for applications where axial shaft expansion is anticipated. In such cases, the N or NU bearing accommodates the shaft expansion. The NUP or NP bearing is considered the fixed bearing because the ribs restrict the axial movement of the rolling element. The fixed bearing is usually placed nearest the drive end of the shaft to minimize alignment variations in the drive. Shaft endplay, or float, is determined by the axial clearance in the fixed bearing.
Types NU , N, NJ, NF , NU P and NP conform to ISO and DIN standards for loose rib rings (thrust collars) and typical industry diameters over or under roller.
The cylindrical roller bearing part numbers are in accordance with ISO 15. They are composed of four digits, the first two digits identify the dimensional series and the last two digits of the part number are the bore size divided by 5. In the dimensional series, the first digit is the width series and the second is the diameter (outer) series. The width series increase width in the sequence 8 0 1 2 3 4 5 6 7. The diameter series increase radial section in the sequence 7 8 9 0 1 2 3 4.
Types having an R prefix are similar in construction to their N counterparts. However, they were designed to conform to ABMA standards.Inch-size bearings are identified by the letter I in the part number. RIU, for example, indicates an inch bearing while RU indicates the equivalent style in metric dimensions