Design variants

Four point contact bearings are available as:

• bearings of basic design ➤ Figure
• bearings with retaining slots in the outer ring ➤ Figure
• X-life bearings ➤ link.

Capable of supporting high axial loads in both directions

Due to the design of the raceways with their high shoulders, the large nominal contact angle of α₀ = 35° and the large number of rolling elements, four point contact bearings have a very high axial load carrying capacity. They are suitable for alternating, purely axial loads or predominantly axial load. The balls are in contact with the inner ring and outer ring each at one point only, as is the case with a single row angular contact ball bearing under axial load➤ Figure.

Four point contact bearings cannot compensate misalignments

Four point contact bearings are not suitable for the compensation of angular misalignments due to housing deformations or shaft deflections. The possible skewing of the inner ring in relation to the outer ring depends, for example, on the bearing load, the operating clearance and the bearing size, and is very small.

Oil or grease lubrication

The bearings are not greased. They must be lubricated with oil or grease.

Compatibility with plastic cages

When using bearings with plastic cages, compatibility between the lubricant and the cage material must be ensured if synthetic oils, lubricating greases with a synthetic oil base or lubricants containing a high proportion of EP additives are used.

Observe oil change intervals

Aged oil and additives in the oil can impair the operating life of plastics at high temperatures. As a result, stipulated oil change intervals must be strictly observed.

The bearings are of an open design

Four point contact bearings are supplied without seals. As a result, sealing of the bearing position must be carried out in the adjacent construction. The sealing system should reliably prevent:

• moisture and contaminants from entering the bearing
• the egress of lubricant from the bearing.

Higher speeds are only possible under purely axial load

Due to the four point contact and resulting higher level of friction, the speed suitability of the bearings is heavily restricted under radial load. High speeds can only be achieved if four point contact ball bearings are subjected to purely axial load.

Limiting speeds and reference speeds in the product tables

Two speeds are generally indicated in the product tables ➤ dimension table:

• the kinematic limiting speed n_G
• the thermal speed rating n_ϑr.

Limiting values

The operating temperature of the bearings is limited by:

• the dimensional stability of the bearing rings and rolling elements
• the cage
• the lubricant.

Solid cages made from brass and polyamide PA66 are used as standard

Standard cages and additional designs for four point contact bearings ➤ Table . Other cage designs are available by agreement. With such cages, however, suitability for high speeds and temperatures as well as the basic load ratings may differ from the values for the bearings with standard cages.

Example of composition of bearing designation

The designation of bearings follows a set model. For an example of this see ➤ Figure . The composition of designations is subject to DIN 623-1 ➤ Figure.

In order to prevent damage due to slippage, a minimum axial load of F_a ≧ 1,2 · F_r is required

In order to ensure low friction in the bearing, especially at high speeds, a minimum axial load is required. In order to prevent an excessive increase in friction in the bearing, the axial force should be sufficiently high that the rolling elements are in contact with the inner and outer ring raceway at only one point. This is ensured if F_a ≧ 1,2 · F_r.

When used as axial bearings, the outer ring must be radially relieved in the housing

If a four point contact bearing is used as a pure axial bearing, the outer ring must have a large radial clearance in the housing, in order that the bearing is not subjected to radial load ➤ Figure.

Support bearing rings over their entire circumference and width

In order to allow full utilisation of the load carrying capacity of the bearings and thus also achieve the requisite rating life, the bearing rings must be rigidly and uniformly supported by means of contact surfaces over their entire circumference and over the entire width of the raceway (not applicable to bearings with radially relieved outer rings). The seating and contact surfaces should not be interrupted by grooves, holes or other recesses. The accuracy of mating parts must meet specific requirements ➤ Table to ➤ Table.

Ra must not be too high

The roughness of the bearing seats must be matched to the tolerance class of the bearings. The mean roughness value Ra must not be too high, in order to maintain the interference loss within limits. The shafts must be ground, while the bores must be precision turned. Guide values as a function of the IT grade of bearing seating surfaces ➤ Table.

Roughness values for cylindrical bearing seating surfaces – guide values

The contact surfaces for the rings must be of sufficient height

The mounting dimensions of the shaft and housing shoulders, and spacer rings etc., must ensure that the contact surfaces for the bearing rings are of sufficient height. However, they must also reliably prevent rotating parts of the bearing from grazing stationary parts. Proven mounting dimensions for the radii and diameters of the abutment shoulders ➤ dimension table. These dimensions are limiting dimensions (maximum or minimum dimensions); the actual values should not be higher or lower than specified.

As the bearings are not self-retaining, they are easy to mount

Four point contact bearings are not self-retaining. As a result, the outer ring with the ball and cage assembly can be mounted separately from the two inner ring halves ➤ section. This gives simplified mounting of the bearings.

The further development of products may also result in technical changes to catalogue products

Of central interest to Schaeffler is the further development and optimisation of its products and the satisfaction of its customers. In order that you, as the customer, can keep yourself optimally informed about the progress that is being made here and with regard to the current technical status of the products, we publish any product changes which differ from the printed version in our electronic product catalogue.