A slewing bearing is a piece of hardware used to facilitate
circular movement, usually of a large device such as a
crane. The term"slew" means to turn without changing
location, so a slewing bearing is onethat will not move
out of place but will instead facilitate movement whilein
one position. These bearings are usually quite large and
are used forheavy-duty applications; they are therefore
usually made from heavy-dutymetals such as steel,
though other materials including aluminum and titanium
can be used for their construction as well.

The slewing bearing isnot mounted on a shaft, but is
instead bolted to a flat surface. The gearsallow one part
of the bearing to move while the other stays in place,
thereby facilitating movement. The path of the movement
can vary;sometimes the slewing bearing is used to
facilitate round movement, while inother cases an
oscillating movement can be performed. The type of
movement depends on the configuration of the slewing
bearing as well asthe location of the gears. The gears
allow a platform to be driven in acertain motion, and the
location of the gears will depend on the design ofthe
device.

The profile of the slewing bearing is usually quite thin,
allowing the distance between platforms to be very narrow.
Ball bearingsare present within the bearing race to
ensure movement is smooth andconstant; these ball
bearings may need to be lubricated or greased
periodically to prevent premature breakdown or abnormal
shaping of theballs. Most devices that use these types of
bearings are quite large andslow-moving, but constant
movement and high temperatures can alter the shapeand
function of the bearings over time, thereby necessitating
maintenance or repair.