A critical component for reducing the wobbling of the shaft along with vibration and
noise is the bearings. Spindle motors have long used ball bearings, which consist of small metal
balls that are housed in a metal ring structure around the spindle motor shaft. However, in the
past few years there has been a transition to fluid dynamic bearings, in which the metal balls are
replaced by high viscosity oil, thereby eliminating the metal-to-metal contact. The advantages
include a further reduction in noise, longer life expectancy and lower cost.