A shaft rotates in a housing on two single row tapered roller bearings mounted in opposition such that the raceways of the one bearing taper downwardly toward the raceways of the other bearing. The metal from which the housing is formed has a higher coefficient of thermal expansion than the metal from which the shaft and bearings are formed. The bearings are set to preload to stabilize the axis of rotation. To prevent the cups (outer races) of the bearings from becoming loose as a consequence of differential thermal expansion between the housing and shaft, the cups are provided with beveled back faces which abut beveled shoulders at the ends of bearing seats in the housing. As the housing expands radially and perhaps eliminates radial interference fits between the cups and housing, the housing also expands axially and maintains the beveled shoulders of the bearing seats firmly abutted against the beveled back faces of the cups, so that the cups do not displace either axially or radially.