Bearing construction is a key difference between vertical motors and horizontal motors that are mounted vertically. Vertical motors typically drive pumps using thrust bearings. Horizontal motors rarely have those types of bearings. Understanding relevant construction and configuration factors is crucial when confronting lubrication-related issues that can be associated with vertical-motor bearings.

Much has been said and done to produce the "perfect" fit for rolling element bearings in motors and other rotating equipment. Assembly of these machines requires that either the inner fit to the shaft (journal) or the outer fit to the housing (bore) is able to slide; so if one fit is tight, the other must be loose. While "tight" and "loose" are relative terms that must be defined in the quest for the perfect fit, any fit that's too loose or too tight can lead to early bearing failure and costly downtime.