Thrust bearings

Due to their specific construction, thrust bearings are optimally suitable for low rotation speeds with low centrifugal forces and greater stiffness.

In relation to the radial ball bearing, the contact angle of thrust bearings is increased to 90° and consequently, only the axial loads occur. The difference with respect to this bearing is reflected in the fact that the load is distributed evenly across all rolling elements.

There are two different variants of thrust bearings: thrust bearings acting on one side and those acting on both sides.

The classical version of the thrust bearing is enhanced by special structure: Thrust angular-contact bearings, pivot bearings or swing bearings. Thrust bearings are often used in combination with radial bearings.

Axial forces require thrust bearings

If the forces to be absorbed by a roller bearing do not act in a radial direction but rather in the direction of an axle or shaft, one talks about axial forces. The function of the bearing with fundamentally different design is to divert these forces. This prevents a displacement in the direction of the axle. Standard radial bearings are designed for absorption of radial forces in particular, but they can also absorb smaller / medium axial forces as well. However, axial forces are sometimes too great for this solution to be meaningful.

The load is distributed evenly across all rolling elements of thrust bearings, which is not the case when radial deep groove ball bearings are used. Due to their special construction, thrust bearings are in particular suitable for those cases in which the rotation speed is low to medium and in which greater stiffness is required.

The application areas can be divided into 2 main cases:

• Example of angular gear drives: Both radial and axial forces occur here. For this reason, a combination of radial and thrust bearings are required in one shaft. The same is true for tooling and packaging machines.
• Example of a crane: Above all, great forces occur in the axial direction, in this case due to crane’s own weight and loads to be lifted. This is a totally different load case: Above all, the shafts or axles must be secured against displacement in the axial direction. For this reason, the rolling elements are arranged in a bearing in a different way, so that they are only exposed to contact forces.

Designs: Thrust bearings are designed either in a form of a ring, looking similar to radial bearings, but with greater dimensions, or for greater loads in a form of a disk. If rollers are required as rolling elements, the permissible rotation speeds are in this case very restricted, due to the fact that not only rolling friction occurs in this case. Even here, the radial loads may by no means be neglected; a combination of radial and thrust bearings on one shaft is obligatory.

Models of thrust bearings

• Thrust deep groove ball bearing: No load in radial direction; suitable for greater rotation speeds.
• Thrust cylinder roller bearings: Capable of bearing great loads in axial direction, shock-proof; also not able to bear loads in radial direction. Not suitable for greater rotation speeds.
• Thrust spherical roller bearings: Can absorb axial and radial forces, also suitable for greater rotation speeds. Can compensate for misalignments. Very robust and commonly used even in case of very large dimensions.
• Thrust needle bearing: Very flat structure,  best suitable for particularly stiff and shock-resistant bearing in case of great axial forces.

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