21
SHARPENING THE SAW CHAIN
If the saw chain was damaged by contacting hard objects, such as
nails or stones, or was abraded by mud or sand on the wood, have
an authorized service dealer sharpen the saw chain.
When sharpening the saw chain, file all cutters to the specified
angles and measurements. Other angles or measurements can
cause excessive wear to the guide bar and saw chain, cause the
chain to dull quickly and increase the chance of kickback. Fast
cutting can be obtained only when all cutters are uniform.
1. Tighten the chain tension so that the saw chain is taut and does
not wobble. Refer to
Adjusting the Chain Tension
.
• Always file the saw chain at the midpoint of the guide bar.
2. Use a round file and file holder (tools not included) to sharpen
the top plate and side plate of each cutter.
• Use a 5/32 inch (4 mm) diameter file when sharpening the 18
inch saw chain (RM4218). Use a 3/16 inch (4.8 mm) diameter
file when sharpening the 20 inch saw chain (RM4620).
• Keep the file level with the top plate of the cutter (Fig. 33). Do
not let the file dip or rock. Use light, but firm pressure.
• File toward the front corner of the cutter (Fig. 34). Lift the file
away from the cutter at the end of the forward stroke. Only file
on the forward stroke.
• Apply a few firm strokes to each tooth. When filed correctly,
the top plate will be at a 30º angle and the side plate will be at
an 80º angle (Fig. 35). Using the correct file and file holder will
automatically produce the correct angles.
• File all the left-hand cutters in one direction (Fig. 34). Then
move to the other side of the saw chain and file all of the right-
hand cutters in the opposite direction (Fig. 34).
• Occasionally remove filings with a wire brush.
3. Use a depth gauge tool (not included) to measure the depth
gauge clearance (Fig. 36) of each cutter. The depth gauge
clearance must be maintained at 1/32 inch (0.6 mm). The depth
gauge clearance determines the depth at which the cutter enters
the wood during operation and the size of the wood chips
produced. Too much clearance increases the chance of
kickback. Too little clearance decreases the size of the wood
chips, thus deceasing the ability to cut.
• Use a 1/32 inch (0.6 mm) depth gauge jointer and a flat file
(tools not included) to lower the depth gauge to the correct
clearance (Fig. 36).
• After lowering the depth gauge, use the flat file to restore the
original rounded shape to the depth gauge (Fig. 37). Take care
not to damage the cutting edges or nearby links.
WARNING:
The saw chain is very sharp. Always wear
heavy-duty protective gloves when handling or performing
maintenance on the saw chain.
CAUTION:
A dull or improperly sharpened saw chain
can cause excessive engine speed during operation, which
can result in severe engine damage.
WARNING:
An improperly sharpened saw chain
increases the chance of kickback. Failure to replace or
properly maintain the saw chain can cause serious injury.
Fig. 33
Depth Gauge
Top Plate
Fig. 34
Filing Angle
Fig. 35
Correct Filing Angles
Top Plate
Fig. 36
Depth Gauge Jointer
Flat File
Side Plate
Depth Gauge Clearance
1/32 inch (0.6 mm)
Right-Hand
Cutters
Left-Hand
Cutters
Side Plate
80º
30º
Summary of Contents for RM4218
Page 27: ...27 NOTES...
