There are three important factors for
proper bearing installation. First, you should use an arbor press to press-fit
the bearings. This is the most efficient installation method and will preserve
the integrity of the bearing. For example, if you use a hammer, the
installation of the bearing might be uneven.
Next, ensure your bearing housing
has a chamfer-plastic bearing manufacturer, igus, recommends 25-30 degrees for
its bearings-and that it is press-fit with the outside chamfer of the bearing
against the housing chamfer (for flange bearings, the sleeve portion will have
Then, ensure your
ID-after-press-fit matches your supplier's recommended tolerances for the
bearing. All measurement testing should be conducted after the bearing is
press-fit into the housing. Prior to press-fitting, the bearing is oversized
and may not conform to the listed specifications.
Conducting quality checks on the
bearings after installation can be done many ways. One way is to use a
pin-gauge test, also called a "go/no-go" test after press-fitting the bearing
into the smallest specified housing-bore dimension. This will make sure the
bearings are within specifications and will work properly once in service. Specifically,
a "go" signifies the pin falling through the bearing under its own
weight, while a "no-go" occurs when the pin does not fall through the
bearing, or "sticks".
A pin-gauge test is the most accurate quality check
because the pin acts like the shaft used in a real-world application and it
reveals the inner diameter of the bearing at the smallest points, which is most
critical to the application.
When using a plastic bearing, a
pin-gauge test works especially well because the peaks and valleys of the
bearing are irrelevant as long as the recommended shafts are able to pass
through the bearing. Over time, as the bearing's self-made lubrication fills in
the peaks and valleys of the shaft and the bearing, an ideal sliding surface is
While there are other tests that
can be used to quality-check a bearing, problems can arise when applying these
methods to plastic bearings. In particular, the use of a caliper should be
avoided. Calipers, depending on the level of accuracy, are generally acceptable
for only hurried quality checks. However, depending on the amount of pressure
applied by the caliper or the location of the measurement, it is possible the
numbers will not read correctly. It is more reliable to use a pin-gauge test to
avoid unforeseen problems.
A common post-installation problem
is the bearing showing signs of material shave-off at installation. If this
occurs, check to make sure the housing has the recommended chamfer of 25-30
degrees. If using a sleeve bearing (which typically has only one end with an
outside chamfer), match up the bearing's outside chamfer with the housing-bore
chamfer. If using a flange bearing, the sleeve portion (installed) has the
outside chamfer already. In both instances, also check the housing bore to
ensure it is not undersized.
Another problem that can occur is
when the bearing is press-fit into the housing bore is that the ID
after-press-fit is smaller or larger than the recommended tolerances. If this
problem arises, the following points need to be assessed:
- Confirm that the housing bore matches the
recommended tolerances (generally an H7 housing bore).
- If the housing bore is comprised of a softer metal,
like aluminum or plastic rather than steel, it is possible that the bearing is
pushing into the housing bore. To compensate, try using a thicker-walled
- Check your shaft tolerances to confirm that your
pin gauges determined during the QC process are accurate.
Tom Miller is Bearings Unit
Manager, North America for igus Inc. He can be reached at firstname.lastname@example.org
- If the ID of the bearing is undersized, make sure
shavings are not in between the bearing and the housing.