For the most accurate measurements,
miniature and instrument ball bearing
dimensions should be measured with a
calibrated air gauge. A good second option
is a calibrated optical comparator.
On occasion, it may be necessary to use
a calibrated, hand-held micrometer to
double-check a measurement or for
simple verification while working in the
field.

While PKB strongly recommends the
use of an air gauge or an optical comparator,
we also understand the usefulness
of a hand-held micrometer in certain
situations.

Using a micrometer on delicate objects—like
miniature and instrument
ball bearings—is very different from
using a micrometer on solid objects.

The reason for this is miniature and
instrument ball bearing rings are usually
quite thin and flexible. Improper
micrometer use may cause ring deformation
and inaccurate micrometer
readings.

To measure a miniature or instrument
ball bearing ring without damaging
or deforming the ring, it is advisable
to use the micrometer as a GO/NO-GO
gauge.
How to check minimum tolerance of
the dimension by using micrometer as
go/no-go gage:

1. Twist the ratchet just until the
micrometer gauge reads the
minimum tolerance for the
dimension to be measured.

a. Do not adjust the micrometer
while the bearing is in between the
anvil and spindle.

b.Do not squeeze the bearing in
between the anvil and spindle
head, as that may distort the ring.

2. Lock the micrometer.

3. Using proper bearing handling
practices, place the bearing
between the anvil and spindle of the
micrometer.

4. Do not force the bearing into the
micrometer.

5.If the bearing does not fit easily into
the micrometer, then the bearing
exceeds the minimum tolerance for
the dimension.

6.If the bearing fits easily into the
micrometer, at the preselected
minimum tolerance setting, then
the bearing is under / less than
the minimum tolerance for the
dimension.

7.Remove the bearing from the
micrometer and set it aside using
proper handling techniques.

How to check maximum tolerance of
dimension by using micrometer as go/
no-go gage:

1. Twist the ratchet just until the
micrometer gauge reads the
maximum tolerance for the
dimension to be measured.
a. Do not adjust the micrometer
while the bearing is in between the
anvil and spindle.

b.Do not squeeze the bearing in
between the anvil and spindle
head as that may distort the ring.

2. Lock the micrometer.

3. Using proper bearing handling
practices, place the bearing
between the anvil and spindle of the
micrometer.

4. Do not force the bearing into the
micrometer.

5.If the bearing does not fit easily into
the micrometer, then the bearing is
larger than the maximum tolerance
for the dimension.
6.If the bearing fits easily into the
micrometer, at the preselected
maximum tolerance setting, then
the ring is within the maximum
tolerance for the dimension.

7.Remove the bearing from the
micrometer and set it aside using
proper handling techniques.
Find this and other valuable bearing
tutorials on our website (www.pacamor.com)
Home Page under “New
PKB Blogs.”