Early linear motion bearings consisted of a row of wooden rods placed under a row of pry bars. The simplest rotary bearing was the bushing bearing, which was simply a bushing sandwiched between a wheel and an axle. This design was later replaced by rolling bearings, which used many cylindrical rollers instead of the bushing, each rolling element acting like an individual wheel.
An early example of a ball bearing was discovered on an ancient Roman ship built in Lake Nami, Italy, around 40 BC: a wooden ball bearing used to support a rotating tabletop.
Modern linear motion bearings use the same working principle, although sometimes balls are used instead of rollers. The bearing materials have also changed. So, do bearings have a shelf life? The answer is yes.
The shelf life of a bearing can be called its "lifespan." Bearing lifespan refers to the number of revolutions or hours a bearing can withstand under a certain load before pitting occurs. Many factors affect bearing lifespan, including the bearing itself and its usage.
