Needle roller / angular contact ball bearings
SKF needle roller / angular contact ball bearings combine a radial needle roller bearing with an angular contact ball bearing. The radial loads are accommodated exclusively by the needle roller bearing and the axial loads exclusively by the angular contact ball bearing. These low cross section bearings can operate at high speeds and accommodate heavy radial and light axial loads. SKF supplies these bearings without seals in the following two series:
NKIA series (fig. 1), bearings can accommodate axial loads in one direction
NKIB series (fig. 2), bearings can accommodate axial loads in both directions
Bearings in both series are separable i.e. the inner ring can be mounted separately from the outer ring, rolling element and cage assemblies. However, the inner rings in the NKIB series are not interchangeable with those from another seemingly identical bearing. Therefore, the bearings must be kept together as supplied.
Depending on the application, needle roller / angular contact ball bearings can be grease or oil lubricated. In the case of grease lubrication, both the needle roller and angular contact ball bearing should be filled with the same lubricant prior to mounting.
Needle roller / angular contact ball bearings in the NKIA 59 series (fig. 1
) can accommodate axial loads in one direction and can, therefore, locate the shaft in one direction only. For short shafts and where changes in length as a result of thermal expansion are relatively minor, two bearings in the NKIA 59 series can be mounted back-to-back (fig. 3
Needle roller / angular contact ball bearings in the NKIB 59 series (fig. 2
) can locate a shaft in both directions. The axial clearance is between 0,08 and 0,25 mm. To facilitate mounting, the bearing has a two-piece inner ring. When mounting the inner ring, it is important that the two pieces are mounted immediately adjacent to each other without any gap between them.
Depending on their design, series and size, SKF needle roller / angular contact ball bearings are fitted with cages shown in table 1.
The lubricants generally used for rolling bearings do not have a detrimental effect on cage properties. However, some synthetic oils and greases with a synthetic oil base and lubricants containing EP additives, when used at high temperatures, can have a detrimental effect on polyamide cages. For additional information about the suitability of cages, refer to Cages and Cage materials.
Depending on the design and size, SKF supplies needle roller bearings with different features to facilitate efficient lubrication and relubrication.
The needle roller bearing of all combined bearings has an annular groove with one lubrication hole in the outer ring.