Idler Wear
Measurement Technique
Tread and center flange wear are the mea-
surable wear positions on idlers.
Tread wear is determined by measuring
with the broad based depth gauge from the
idler center flange to tread surface. The
positioning of the depth gauge should be
so that the measurement rule is aimed as
closely as possible toward the center of the
idler with the base flat on center flange
and parallel to idler shaft. The greatest
error in measuring idler tread wear arises
from wear on top of the center flange
which alters the reference point. If this
wear is suspected some attempt to com-
pensate for it should be made in the
reading taken. Remember idler tread wear
measurements increase as tread wear
occurs and decreases as center flange wear
occurs.
Center flange wear is measurable with the
ultrasonic wear indicator on fabricated
idlers only. It measures the thickness of
the center flange and should be taken
directly in the center of the flange. Use the
conventional depth gauge to measure wear
on the tread surface, then add the center
flange wear to the depth gauge measure-
ment before determining percent worn.
Wear Limits
Idler tread allowable wear and resulting
wear limits are based on two basic criteria:
Rebuildability of the tread surface plus
center flange to track bushing clearance.
As wear proceeds past 100 percent each of
these considerations may result in damage
to other parts. If the idler is worn beyond
120 percent the tread will become too thin
to successfully rebuild.
Wear Charts
Wear charts for idlers are direct reading
from the measurement taken. They have a
built-in factor allowing for faster wear rate
after the hardened case depth is worn
away. As with links and rollers, the wear
rate is about three times as fast in the
unhardened material below the case depth.
Rebuildability
Idler tread and flange can be successfully
rebuilt (welded) several times if they are
not worn beyond service limits and if
center flange wear is considered into this
service point.
Welded idlers generally provide wear life
equal to original tread wear life to respec-
tive limits if welded to original dimensions.
Swapping Idlers
Idlers can be swapped from side to side or
front to rear (on elevated sprocket machines)
to balance wear. Consider swapping
whenever the ratio of most worn to least
worn is greater than 1.5 to 1 and the average
percent worn is less than 60 percent.
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IDLERS
General Information