The bearing arrangement of a rotating shaft requires two
bearings to locate and support the shaft radially and axially.
In most applications one of the bearings locates the shaft
both radially and axially. The second bearing provides purely
radial support. These are known as locating and non-locating
or "fixed" and "free" bearings.
Locating (fixed) bearings
The locating bearing must be capable of carrying combined
loads in both directions and must also be secured to both
the shaft and housing to prevent lateral movement. Suitable
bearings for this purpose are deep groove ball, spherical
roller, double row or paired angular contact ball or paired
taper roller bearings. In some instances a purely radial bearing
such as a cylindrical roller bearing without flanges can be
used if paired with a thrust bearing having radial clearance
in the housing.
Non-locating bearings provide radial support only and must
allow the shaft relative movement to the locating or fixed
bearing to allow thermally induced dimensional changes. This
can take place within the bearing itself, as in a cylindrical
roller bearing, or between one of the bearing rings and its
In some applications both bearings are used to locate the
shaft axially. All types of radial ball and roller bearings,
which can accept axial loads in at least one direction, can
be included in this category. In these instances the effect
of thermal expansion within the bearings and shaft assembly
must be provided for when fitting the bearings.