Ball versus roller load capacity and speed
Bearings support rotating shafts with minimal friction using rolling elements to convert sliding friction into rolling friction. Ball bearings use spherical elements, distributing loads over contact points and permitting high-speed rotation with moderate load capacity. Roller bearings use cylindrical or tapered rollers, concentrating loads along lines, and handle much higher loads but at lower speeds due to friction. Tapered roller bearings resist both radial and axial loads, suited to wheel hubs and machine spindles.
Journal and thrust bearing specializations
Journal bearings support radial (perpendicular to axis) loads; thrust bearings resist axial (along axis) loads. Most applications use journal bearings; thrust bearings appear where axial movement is restricted (pump shafts, vertical turbines). Hybrid arrangements stack multiple bearing types in one housing to handle combined radial and thrust loads. Preloading (applying slight compression during assembly) reduces internal clearance and improves stiffness in precision applications.
Material, lubrication, and service life
Bearing material (hardened steel for most, ceramic hybrid for high speed) directly affects load rating and life. Lubrication (grease or oil) controls friction and heat generation. The L10 life (bearing life with 90 percent survival at nominal load) guides replacement schedules. Misalignment, contamination, and inadequate lubrication drastically reduce bearing life, making condition monitoring (temperature, vibration, noise) essential in critical machinery.