Four-point contact bearings

Description

Four-point contact bearings are single row angular contact ball bearings and can carry high axial forces in both directions. However, radial force absorption is low. Four-point contact bearings are frequently employed solely as axial bearings, and, for this purpose, combined with a radial bearing.

Dimensions/standards

In four-point contact bearings, the main dimensions are standardized according to ISO 15 (Radial bearings – boundary dimensions), DIN 616 (Roller bearings – boundary dimensions) or DIN 628-4 (Radial angular contact ball bearings – four-point contact bearings). Retaining grooves: ISO 20515:2012 or DIN 5412-1:2000

Tolerances

Four-point contact bearings are designed with standard tolerances (PN) according to DIN 620-2 (Roller bearing tolerances – tolerances for radial bearings).

Bearing design types

SLF manufactures the four-point contact bearings in two design types:
with split inner ring as QJ design and with split outer ring as Q design, each in the 2 and 3 series.

The split inner or outer ring makes it possible to accommodate a large number of balls. The corresponding ring (outer or inner ring) with the ball and cage assembly and the corresponding ring halves can be mounted separately. Angular adjustability is minimal.
The bearings in the QJ design have a contact angle of 35°, in the Q design, of 23°.

Clearance

Axial clearance in the standard design CN is according to ISO 5753-2 (Roller bearings – clearance – axial clearance) and DIN 628-4 (Roller bearings – radial angular contact ball bearings – four-point contact bearings). Other designs can be supplied upon request.

Cage

Four-point contact bearings are manufactured with solid brass cages or cages made of fiberglass-reinforced polyamide 66. The product portfolio indicates which design is available as standard. Please contact us regarding divergences from standard. The operating temperature of the polyamide cage is maximum 120 °C.

Working temperature

SLF-four-point contact bearings with a maximum outer diameter of 240 mm are standard stabilized in dimensions by S0, meaning that they are heat treated to make them usable up to 150 °C working temperature. Above a 240 mm outer diameter, the four-point contact bearings are standard stabilized in dimensions by S1, meaning they are heat treated to make them usable up to a working temperature of 200 °C. However, as a rule, the maximum working temperature is not limited by the dimensional stability of the bearing rings and balls. Frequently the cage, seals, or the lubricant are the limiting factors. Please find the relevant information regarding this subject in the corresponding chapters. If you are uncertain or have specific questions regarding the temperature limits of our bearings, then the SLF team is available to support you.

Greasing/lubrication & sealing

Four-point contact bearings are manufactured without seals; consequently, the bearing location must be sealed around/ on the surrounding components. The sealing must ensure that no moisture and contaminants enter the bearing, and that no lubricant is lost. The four-point contact bearings are delivered ungreased but must be lubricated with oil or grease. Choose the lubricant according to the application.

Dimensioning

Dynamic equivalent load

For lifetime calculation, an equivalent radial load must be inserted in case of combined load. This is determined as follows:

\(\)
$$P = F_r + 0,66 * F_a$$ for $$\frac{F_a}{F_r} \leq{0,95}$$
$$P = 0,6 * F_r + 1,07 * F_a$$ for $$\frac{F_a}{F_r} > 0,95$$
P dynamic equivalent load (radial and axial load) [kN]
Fr radial dynamic load [kN]
Fa axial dynamic load [kN]

Static equivalent load

To assess the static load safety factor for combined load, determine the equivalent radial load as shown below:

\(\)$$P_0 = F_{0r} + 0,58 * F_{0a}$$
P static equivalent load (radial and axial load) [kN]
F0r radial static load [kN]
F0a axial static load [kN]

Static load safety factor

For four-point contact bearings subjected to static load, always inspect the static load safety factor S0 in addition to the nominal lifetime L (L10h).

\(\)$$S_0 = \frac{C_0}{P_0}$$
S0 static load safety factor [-]
C0 static load rating [kN]
P0 static equivalent load [kN]

Required minimum load

An axial minimum load is required to ensure low friction inside the bearing, first of all in case of high speeds. Increase in friction inside the bearing should be moderate. For this reason, the axial force must be so high that the rolling elements contact the raceways of the inner and outer rings in only one point. This is achieved, if

\(\)$$F_a ≥ 1,2 * F_r$$