Rolling-ring bearings are basically standard ball bearings but with a ridge machined into the inner race. Just the ridge apex makes contact with a smooth, threadless shaft inserted in the bearing bore. The resulting clearance permits angling the bearing left or right while maintaining continuous point contact with the shaft surface.

Changing the bearing angle relative to the shaft centerline determines bearing carrier travel direction and pitch, the distance traveled per shaft revolution. Angle changes, and hence speed and direction changes of the bearing carrier, can be done on the fly while the shaft rotates at constant speed. Rolling-ring actuators give backlash-free linear motion resolvable to 0.0004 in. for reciprocating, positioning, and indexing applications.