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Groove depth
As the rails wear the bar groove
becomes shallower. A minimum
depth must be maintained in order
to ensure that the drive link tangs do
not scrape along the bottom of the
groove:
Chain pitch
Minimum groove
depth
1/4" P
4 mm
1/4"
4 mm
3/8" P
5 mm
.325"
6 mm
3/8"
6 mm
.404"
7 mm
The cutters and tie straps will not
otherwise ride on the rails.
Checking groove depth
Rollomatic guide bars
Use the scale (groove cleaner) on a
filing gauge to check the groove
depth on the top and the bottom of
the guide bar.
Duromatic guide bars
Use the scale (groove cleaner) on a
filing gauge to check the groove
depth over its entire length.
If the measured depth is less than
specified, the guide bar must be
replaced.
44
4.7
Repairing
4.7.1
Bar Rails, Removing
Burrs
The bar rails wear and burrs form on
their outside edges. Remove the
burrs with a grinding wheel or a belt
grinder, guide bar dresser or a
sharpening file (flat or triangular)
A belt grinder with a stop is required
to level bar rails that have worn
unevenly, e.g. because of an
incorrectly sharpened chain.
4.7.2
Opening the Groove
Recommended only for minor
pinched areas of bar.
Clamp the guide bar in a vise.
Insert a groove drift which matches
the specified groove width in the
groove at an angle of about 45° at a
point where the width is still correct.
Use a hammer to knock the groove
drift through the pinched portion of
the groove.
Repeat this process several times
until a chain with the correct drive
link gauge and, on a Rollomatic bar,
the right pitch can be pulled around
the whole bar without resistance.
Examine the whole bar for any signs
of cracks, especially at the point of
deformation. If any cracks are
found, the guide bar must be
replaced to avoid any risk of injury.
4.7.3
Replacing the Nose
Sprocket
a
Replace the nose sprocket if:
– there is no clearance "a" between
the chain and bar nose – teeth of
nose sprocket are worn – or
– the roller bearing is damaged.
Chain and Bar Manual
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