The Differences between Ball Bearings and Sleeve Bearings

A ball bearing is a type of rolling-element bearing that features an inner and outer race with a series of balls placed between the two. As the balls maintain the separation between bearing races, they also reduce the rotational friction of an assembly and may take on radial and axial loads. With the rotating race attached to the rotating assembly, the balls will move alongside it and cause a lower coefficient of friction as compared to two flat surfaces rubbing against one another. For the construction of the ball bearing, hardened steel often serves as the main material used for much of the assembly. Sleeve bearings, on the other hand, are types that feature sleeves that reduce vibrations between linear moving parts and absorb their friction through sliding motions. Often, the sleeve of the sleeve bearing is constructed from metal, plastic, or a fiber-reinforced composite sleeve.

 
Ball bearings in particular require simple lubrication types for their operation, and their lower contact area as compared to sleeve bearings means that they produce less heat. With their smaller size, they can also be useful for more compact housing assemblies, though this makes their shaft deflection lower. For their applications, the ball bearing is quite suitable for angular contacts, and they can undertake both thrust and radial loads. If there is a need for increased thrust load carrying capacity, such bearings can be arranged in tandem.
 
Despite their advantages, ball bearings do lack in some ways that can make them less fit for certain applications. With their limited thrust capacity and operating speeds, the ball bearing is not often used for high speed centrifugal pumps. With more moving parts within the assembly, the ball bearing may exhibit a shorter lifespan. Additionally, premature failures are possible, though not common, and can result in high amounts of rotor vibrations.
 
With sleeve bearings, an extreme amount of radial thrust capacity is provided, though such bearings most often serve moderate to high-speed applications. With more stiffness, split halves, and easy replacement as compared to ball bearings, the sleeve bearing may be a good choice for certain assemblies. Despite this, sleeve bearings are more expensive, and they cannot take on axial thrust loads by themselves. Sleeve bearings are also not optimal for low-speed applications, often performing much better with higher speeds. Lastly, their increased friction losses and size require that they have more lubrication to mitigate generated heat during standard operations.