NCCER Millwright Practice Exam

The self-aligning bearing is characterized by its unique design, which includes an outer race that is a section of a sphere. This spherical outer race allows the bearing to accommodate misalignment between the shaft and the housing. As the shaft rotates, the inner race and rolling elements can move within the outer race, allowing for adjustments in alignment without causing excessive wear or failure.

This type of bearing is particularly beneficial in applications where there is potential for shaft displacement due to thermal expansions, vibrations, or manufacturing tolerances. The self-aligning feature helps maintain smooth operation and extends the bearing's lifespan, making it a valuable choice in many mechanical assemblies.

In contrast, thrust bearings typically support loads along the shaft axis and do not have a spherical outer race; ball and roller bearings have cylindrical or toroidal shapes designed primarily for radial loads with limited capability for misalignment.