Thrust Roller Bearings - Flat-race And One-directional Grooved-race Design | Supports Pure Thrust Loads, Allows Eccentricities, High Contact Stresses

In a sense, thrust bearings are 90A angular-contact bearings. Thrust bearings support pure thrust loads at moderate speeds, but for practical purposes, their radial load capacity is nil.
Because thrust bearings cannot support radial loads, ball thrust bearings must be used with radial bearings. Even slight misalignments can cause drastic load concentrations, so the thrust bearings must be kept square with the shaft or used with self-aligning seats. However, the ability of the self-aligning seat to follow shaft wobble or misalignments is still quite limited.

Flat-race thrust bearings consist of a pair of flat washers separated by the ball complement and a shaft-piloted retainer, so load capacity is limited. Contact stresses are high and torque resistance is low.
The prime advantage of flat-race thrust bearings is they permit eccentricities, because there are no grooves to restrain one race from wandering slightly with respect to the other.

One-directional, grooved-race thrust bearings have grooved races very similar to those in radial bearings. Thrust bearing capacity is about twice that of the flat-race bearing and limiting speed is about three times as high. However, a thrust bearing has a limiting speed, which is still quite low because balls spin at high speeds.