Angular Contact Ball Bearings

Single row angular contact ball bearings feature angular raceways of inner and outer ring and a resulting force-transferring contact angle. Due to this, an axial load always induces a radial load and the other way around, which is why angular contact ball bearings are always combined with a second bearing. Paired, they can in addition to radial forces also absorb axial and combined forces and are particularly suitable for high speeds. Single row angular contact ball bearings cannot be disassembled.

Single row angular contact ball bearings are of limited suitability for compensation of misalignments. The admissible misalignment between inner and outer ring depends on the bearing size, the internal bearing design, the clearance fit, and the acting of forces and moments. Misalignments cause harmful ball movement and produce additional stresses in the bearing which reduce its operating life.

KRW distinguishes between kinematic limiting speed n_G and thermal reference speed n_th. The kinematic limiting speed is a practical mechanical limit value and is based on the mechanical fatigue strength of the rolling bearing as a function of its installation situation and lubrication. The limit speed must not be exceeded even under optimum operating conditions without prior consultation with KRW.

The thermal reference speed represents the equilibrium between the heat generated in the bearing by friction and the heat flow dissipated. It is standardised in DIN ISO 15312 (Rolling bearings - Thermal reference speed).

For dynamically loaded bearings

The service life formula according to ISO 281 L₁₀ = (C/P)^p for dynamically loaded bearings requires an equivalent load (P) from constant direction and size. To calculate P, calculation factors and the ratio of axial and radial load are required. This is shown in the following equations.

Equivalent Dynamic Bearing Load P

a) Single bearings and tandem arrangement

The equivalent bearing load P for dynamically loaded single bearings or bearings in tandem arrangement depends on the ratio F_a/F_r (axial force / radial force). The equivalent dynamic bearing load can then be determined using the following formula:

b) O- and X-arrangement

The equivalent bearing load P for dynamically loaded bearings in O- or X-arrangement depends on the ratio F_a/F_r (axial force / radial force). The equivalent dynamic bearing load can then be determined using the following formula:

Resulting axial force for O- and X-arranged roller bearings

Due to the angular raceways, when a radial force occurs, angular contact ball bearings generate an axial reactive force which is relevant to the bearing dimensioning. When a shaft is supported by two identical or differently sized angular contact ball bearings, the radial load of one bearing produces an axial load for the other bearing. This internal resulting force must be considered when determining the total axial load. The value of the total axial load on a single bearing is determined with the following formulas:

To the formulas applies that the bearings being affected by the outer axial force K_a are marked with A and the counter bearings with B. All bearings are backlash-free and considered without preload.

c) Reduction of dynamic load rating in a bearing set

For identical angular contact ball bearings assembled directly side by side in X-, O-, or tandem arrangement, the load rating of the bearing set must be reduced. For the dynamic load rating, the following correlation applies:

Dynamic dimensioning loses its validity for bearings rotating at very low speeds (n x d_m ≤ 4000 mm/min). The static load safety factor S₀ is calculated as follows:

Static load capacity

a) single bearings or tandem arrangement

For statically loaded single row or tandem arranged angular contact ball bearings, the following correlations apply:

b) X- und O-arrangement

For statically loaded angular contact ball bearings in X- or O-arrangement, the following correlations apply:

c) Reduction of static load rating in a bearing set

For identical angular contact ball bearings assembled directly side by side in X-, O-, or tandem arrangement, the load rating of the bearing set must be calculated. For the static load rating, the following correlation applies:

A minimum load is required for the reliable operation of a rolling bearing. If the minimum load is not reached, slippage may occur. The minimum radial load for angular contact ball bearings is roughly assumed to be 1% of the static load rating C₀ of the bearing. If the value falls below this value, consult KRW Application Engineering.