Deep Groove Ball Bearings

Deep groove ball bearings are the most commonly used type of rolling bearings. In addition to radial forces, they can also absorb axial and combined forces and are particularly suitable for high speeds. Deep groove ball bearings cannot be disassembled and only allow a small tilting angle.

Deep groove ball bearings are non-latching bearings that cannot be disassembled. In addition to radial forces, they also absorb axial forces from both directions. Depending on bearing clearance, contact angles are adjusted in the process. The radial load limit for ball bearings is significantly lower than for roller bearings with line contact due to the point contact.

Deep groove 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.

Equivalent Dynamic Bearing Load P

For a purely radially loaded deep groove ball bearing acting as a floating bearing, the following applies:

The equivalent bearing service life for axially loaded deep groove ball bearings 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:

The calculation factors X and Y depend on the ratio:

The absorption of axial forces is related to the contact angle of the bearing which is adjusted by the operating bearing clearance. The factors e, X, and Y can be taken form the following table depending on the bearing clearance.

If a calculated value lies between the specified values, the surrounding values must be taken and interpolated to the desired value. The table values only apply to the fits shaft: j5 to k5, housing: J6.

For statically loaded bearings

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:

Minimum Radial Load

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 deep groove 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.