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Needle roller / cylindrical roller thrust bearings

fig. 1
SKF supplies needle roller / cylindrical roller thrust bearings in the NKXR series (fig. 1).

These combined bearings:

  • consist of a radial needle roller bearing and a cylindrical roller thrust bearing
    The cylindrical roller and cage thrust assembly is identical to the 811 series.
  • are supplied without an inner ring
  • can be combined with an inner ring (fig. 2), where the shaft cannot be hardened and ground (→ product table, must be ordered separately)
  • can accommodate axial loads in one direction
  • can locate the shaft in one direction only
  • can be mounted back-to-back (fig. 3) for short shafts and where changes in length due to thermal expansion are relatively minor
    For these types of arrangements, SKF recommends preloading the thrust ball bearings with Belleville washers (cup springs). This elastic preload helps to prevent the balls from skidding if one of the thrust bearings becomes unloaded. Preload also improves performance of the thrust ball bearings while reducing noise levels.
NKXR series bearings
  • are separable (fig. 1)
  • can be mounted separately from both the cylindrical roller and cage thrust assembly and the shaft washer
  • should be oil lubricated, as oil facilitates an adequate supply of lubricant to the bearing
  • have no stamped steel cover, as standard
  • have a stamped steel cover for bearings with designation suffix Z (fig. 4) that
    • has no lubrication holes
    • extends over the shaft washer of the cylindrical roller thrust bearing
    • is firmly attached to the housing washer that is integral to the needle roller bearing outer ring
    • makes these bearings non-separable
Sealing solutions

SKF supplies certain needle roller / cylindrical roller thrust bearings capped with a stamped steel cover over the thrust part of the bearing (fig. 4, designation suffix Z). The cover, which has no lubrication holes, forms a gap-type seal to retain the grease in the bearing.

When capped bearings must operate under certain conditions, such as very high speeds or high temperatures, some grease may leak. For bearing arrangements where this would be detrimental, appropriate actions could be taken.

Greases for capped bearings

The thrust part of combined needle roller bearings with the designation suffix Z is supplied greased as standard. They are filled with high-quality grease (table 1) under clean conditions.

The relatively large quantity of grease in the bearings means they can be operated for long periods before relubrication is required (→ Perform calculations). SKF recommends SKF LGWA 2 grease (table 1), if relubrication is required.

Relubrication features

The needle roller bearing used in combined bearings has an annular groove with one lubrication hole in the outer ring.

Cages

SKF needle roller / cylindrical roller thrust bearings are fitted with cages shown in table 2.

When used at high temperatures, some lubricants can have a detrimental effect on polyamide cages. For additional information about the suitability of cages, refer to Cages.

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