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Part 1: Bearing Geometry
By Simon Harrison, Ph.D.
deep-groove ball bearings are made to extremely high levels of precision
and have an OD of 1/2 inch or less. Because of their small size,
these bearings are generally used in applications where accurate,
repeatable rotational performance and low torque are a necessity
and load carrying capacity is a secondary issue. Miniature
bearings are typically used in disk drives, positioning systems,
medical equipment, guidance system components and other high-precision
In order to optimize a design using miniature bearings, it is necessary to consider how the internal geometry of the bearings affects their performance in an assembly. This article addresses some fundamentals of bearing geometry and its implications on performance that an engineer might want to consider in selecting and using a particular miniature bearing.
Radial Play and Contact Angle
a single-row deep-groove ball bearing, one of the major design
parameters is radial play. This is defined as the maximum distance
that one bearing ring can be displaced relative to the other ring
in a direction perpendicular to the axis of rotation of the bearing.
play can be thought of as the natural looseness of the bearing.
The amount of looseness is controlled during manufacture and is
specified by the user through selection of a given radial play
for the bearing. Radial play is an important factor in the performance
of a bearing since it affects the contact angle between the balls
and the raceways.