Support movement and transmit loads.
A bearing constrains movement in some directions while allowing the intended motion. Shaft bearings transfer loads into a housing while allowing rotation.
Bearings are found in motors, sheaves and gearboxes. They help maintain alignment as well as reducing resistance to motion.
Inside a typical rolling bearing.
- Rings and racewaysProvide tracks and transfer loads.
- Balls or rollersRoll between the raceways.
- CageSeparates and guides rolling elements.
Rolling contact usually reduces resistance compared with an equivalent sliding support, but it is not friction-free. Contact deformation, sliding, lubricant and seals all contribute to losses.
Radial and axial describe load direction.
A radial load acts across the shaft, perpendicular to its axis. An axial or thrust load acts along the shaft. Some applications impose both.
Different bearing designs carry different combinations of load. Physical size alone does not determine whether a bearing suits the duty.
Not every bearing contains balls.
A plain bearing supports motion through a sliding interface. Its materials and lubrication arrangement are selected for the load, speed and environment.
Plain and rolling bearings are alternative approaches, not a simple good-versus-bad choice. Some plain bearings use self-lubricating materials; others rely on a supplied lubricant film.
Condition depends on the whole installation.
Load, alignment, contamination, lubrication and temperature affect service life. Damage can produce noise, vibration or increased resistance, but a noise alone does not identify its source.
An inspection considers the bearing alongside the shaft, housing and connected machinery. Replacement needs the correct specification, fit and installation method.
A closer look
A bearing arrangement must locate the shaft while allowing for effects such as thermal expansion where the design requires it. Excessive constraint or incorrect clearance can introduce loads that were not intended.
Check your understanding
Does “radial load” mean a force acting along the shaft?
Reveal the explanation
No. Radial load acts perpendicular to the shaft axis. Axial load acts along it.