Thrust bearing
How does a thrust bearing work?
Thrust bearings are rolling bearings that accommodate axial loads. These forces act parallel to the shaft axis and, depending on the bearing design, can be accommodated from one or both directions.
The thrust bearing consists of two horizontal washers with rolling elements between them. These may either be guided by a raceway or groove (e.g. 5-series thrust ball bearings) or unguided (e.g. thrust needle roller bearings). The two washers may be separate (separable bearing) or secured to prevent the bearing from coming apart (e.g. AX series).
Compared with a radial ball bearing, the contact angle of a thrust bearing is increased to 90° (the self-aligning movement of a spherical roller thrust bearing may cause it to deviate slightly from this angle), meaning that only axial loads occur. Another difference compared with a radial bearing is that all rolling elements carry the load evenly.
What are axial forces?
Axial forces are forces that act parallel to the shaft axis.
Where are thrust bearings used?
Single-direction thrust bearings are suitable for use in applications such as valves and lifting cylinders. Double-direction bearings are used, for example, in machine tools or cranes, where axial loads frequently alternate between tensile and compressive directions.
Due to their design, thrust bearings are only suitable for low rotational speeds with low centrifugal forces, but they achieve very high rigidity and transmit high loads. The minimum load required by thrust bearings increases as the rotational speed rises. Because the washers rest loosely on the rolling elements, centrifugal forces push the rolling elements outward, which in turn determines the required axial load.
What types of thrust bearings are available?
Thrust bearings are designed either as rings or, for higher loads, as washers. The rolling elements may be balls (thrust deep-groove ball bearings, angular contact thrust ball bearings), rollers (cylindrical roller thrust bearings), or needles (thrust needle roller bearings).
Thrust bearings are divided into the following subgroups based on the rolling elements used:
- Thrust deep-groove ball bearings with rigid, separable grooved bearings and washer-shaped raceways
- Cylindrical roller thrust bearings for high axial forces and shock loads
- Spherical roller thrust bearings that can also accommodate limited radial forces
- Thrust needle roller bearings for rigid bearing arrangements in confined spaces
- Combined radial/thrust bearings as an integrated assembly
- Glossary
