Design of bearing arrangements

Used as a thrust bearing

Four-point contact ball bearings are often used as pure thrust bearings, together with a radial bearing. When used in this way, the bearing should be mounted with radial clearance in the housing (fig. 1).

When a four-point contact ball bearing is used together with a cylindrical roller bearing, the radial internal clearance of the cylindrical roller bearing should be smaller than the theoretical radial internal clearance of the four-point contact ball bearing after both have been mounted. The theoretical radial clearance can be calculated from

Cr = 0,7 Ca

Cr=theoretical radial internal clearance
Ca=axial internal clearance (table 1)
The outer ring of the four-point contact ball bearing must be able to accommodate thermal movements. Therefore, it should not be clamped axially, but a small gap should be maintained between the outer ring and the cover flange. To prevent the outer ring from turning, bearings with locating slots should be used (fig. 1). If clamping the outer ring cannot be avoided, the outer ring must be carefully centred during mounting.

Vertical shafts

When four-point contact ball bearings with a machined brass cage (designation suffix MA) are used on a vertical shaft, the limiting speed should be reduced to 70% of the value listed in the product table. As with all vertical shafts, be sure that the bearings are adequately lubricated.

Load ratio

Four-point contact ball bearings do not function properly unless the balls contact only one inner ring raceway and the opposite side of the outer ring raceway. This is the case when the load ratio
  • Fa/Fr ≥ 1,27 for bearings in the QJ 2, QJ 3 and QJ 10 series
  • Fa/Fr ≥ 1,78 for bearings in the QJ 12 series
A load ratio smaller than recommended can reduce bearing service life.
SKF logo