Advantages of the
Depth Gauge Method
(A) Absolutely insures vertical position is
being measured (unless measured at a
point where track is bent).
(B) Averages diameter measurement of
two adjacent bushings for greater
accuracy.
(C) Backside of bushing can be measured
after bushing turn (the importance of
this will be explained in the next
discussion).
3. Ultrasonic Wear Indicator Method
This method is the most accurate because
it directly measures the most critical
dimension, bushing wall thickness. It also
can be used to accurately measure the
backside of bushings after a bushing turn.
Measure the bushing wall thickness by
slowly sliding the probe around the
reverse, vertical, and forward drive sides.
Use the smallest dimension to determine
percent worn.
Sealed and Lubricated Track
Bushing Wear
Measurement Positions
Refer to individual product sections for
specific guidelines.
Wear Limits — Greater and Lesser
Wear limits for Sealed and Lubricated Track
bushings are determined by remaining crack
resistance strength. Two percent worn
columns titled “lesser allowable wear” and
“greater allowable wear” are provided in
bushing wear charts. At 100 percent worn,
the lesser allowable wear column pro-
vides more bushing wall thickness than the
greater allowable wear column. Note, for
example, in the wear charts under the ultra-
sonic measurements, the bushing wall is
always thicker, and thus more crack resis-
tant, on the lesser allowable wear column
than on the greater.
The selection of the optimum allowable
wear column will maximize the link and
bushing life while preventing bushing
cracking. The “optimum” percent worn
column depends on the relative bushing
crack resistance required in your situation.
The amount of required crack resistance
depends on several factors including
sprocket position (high or low), underfoot
conditions, bushing projected life, and
application. Refer to the management
section in front of each product section for
the criteria to use in selecting which allow-
able wear chart to use.
Wear Charts
The expected wear rate through the allow-
able wear limit is determined from several
tests. These rates are built into the wear
charts so that accurate projection to 100 per-
cent worn and 120 percent can be made
assuming uniform abrasive, impact and
other conditions will continue. The built-in
bushing wear rate after the hardened case has
been completely worn through is approxi-
mately 2 times the rate expected in the hard-
ened case depth.
Like with most other components, projec-
tions made to the service points based on
less than 30 percent worn will not be
accurate. The wear charts provide the
percent worn equivalent for those mea-
surements less than 30 percent only for
projecting re-visit or re-measurement
points. The bushing is the most likely
component to use for this re-measurement
projection.
38
SEALED & LUBRICATED TRACK PINS & BUSHINGS
General Information