Figure 19-8. Typical Locations of Antifriction Bearings.
seizure, making it necessary to take the machine out of
ball bearings, such as
operation for immediate repairs.
those shown in C, figure 19-9, have substantial thrust
capacity and provide rigid lengthwise support in one
a. Ball A bail bearing consists of a grooved inner
direction only. Also available are double-row, angular-
race and outer race with a number of balls spaced by a
contact bearings that have high combined load capacity
suitable cage or retainer between them. They are made
with rigid lengthwise support in both directions.
with either a single or double row of balls. Ball bearings
for various purposes differ considerably in the details of
Thrust bearings of the so-called flat type, such as those
their constuction but are of three general types: radial,
shown in D, figure 19-9, have a contact angle of 90
thrust, and angular. These terms are descriptive of the
degrees, or a load line between ball and race that is
direction at which the load is applied to the bearing and
parallel with the axis of the shaft. The small-bore race is
the angle of contact between the balls and races
secured to the shaft and the large-bore race is supported
designed to resist that load.
by the housing. Thrust in one direction presses the races
and balls together; thrust in the other direction separates
A single-row radial ball bearing is shown in A, figure 19-9.
them. Therefore, this type is essen- tially a one-direction
This bearing has radial contact between balls and races,
thrust bearing. Thrust in both directions necessitates the
and is designed pri- marily to resist radial loads, but also
use of duplicate units or a bearing of the double-direction
provides for lengthwise stability where moderate
thrust type. Such bearings are suitable for limited
lengthwise displacement is permissible. It is suitable for
speeds and minimum lengthwise displacement.
usual combined radial and thrust loads and for high
b. Roller. As in the case of ball bearings, the details
of construction of roller bearings vary considerably for
The double-row radial ball bearing shown in B, figure 19-
Like ball bearings, they are
9 is suitable for heavy combined radial and thrust loads,
designed for radial, thrust, and combined loads. Roller
medium speed, and close control of endwise movement
bearings, which have greater contact area than ball
under reversing thrust.
bearings, are used for heavy-duty applications.