Roller bearings are used in spindle applications that require a high level of radial load capacity. Some examples of this are large centerless grinding spindles, large low speed milling spindles and spindles that have radial loads from drive belts.
The drawback to roller bearings is low to no axial load capacity and low speed capacity.
Spindle roller bearings can be mounted using two different methods. Straight bore rollers slide onto the shaft and rely on the size of the shaft and housing to preload the bearing. Tapered roller bearings have a tapered race ID that matches a taper on the shaft. The farther up the taper the bearing is placed the more the inner race expands which increases the preload. Different materials are used in the raceways and rolling elements to increase the speed capability of the bearing. It is extremely important to replace spindle roller bearings with a style that meets or exceeds the applications requirements or premature failure can occur.