27
7-1. Sharpening the saw chain
CAUTION: Before doing any work on the guide
bar or chain, always switch off the engine
and pull the plug cap off the spark plug (see
7‑6 “Replacing the spark plug”). Always wear
protective gloves!
(Fig. 59)
The chain needs sharpening when:
The sawdust produced when sawing damp wood looks like
wood flour.
The chain penetrates the wood only under great pressure.
The cutting edge is visibly damaged.
The saw is pulled to the left or right when sawing. This is
caused by uneven sharpening of the chain.
Important: Sharpen frequently, but without removing too
much metal!
Generally, 2 or 3 strokes of the file will be enough.
Have the chain resharpened at a service center when you
have already sharpened it yourself several times.
Proper sharpening:
CAUTION: Use only chains and guide bars designed for
this saw (see 10 “Extract from the spare parts list”)!
(Fig. 60)
All cutters must be of the same length (dimension a). Cutters
with different lengths result in rough running of the chain and
can cause cracks in the chain.
The minimum cutter length: 3 mm. Do not resharpen the chain
when the minimum cutter length has been reached; at this
point, the chain must be replaced (see 10 “Extract from the
spare parts list” and 7‑4 “Replacing the saw chain”).
The depth of the cut is determined by the difference in height
between the depth limiter (round nose) and the cutting edge.
The best results are obtained with a depth‑limiter depth of
0.64 mm (.025”).
CAUTION: Excessive depth increases
the risk of kickback!
(Fig. 61)
The sharpening angle (
α
) must be identical for all cutters!
30° for chain type 092 (91VG), 492 (91PX), 290 (90SG),
291 (90PX)
The teeth will have the proper angle (
ß
) automatically if the
proper round file is used.
80° for chain type 092 (91VG), 492 (91PX)
75° for chain type 290 (90SG), 291 (90PX)
Different angles result in a roughly, irregularly running chain,
increase wear and tear and cause chain beakage.
Files and how to work with them
Use a special saw chain round file for sharpening. Standard
round files are unsuitable. See 10 “Extract from the spare parts
list”.
Type 092 (91VG), 492 (91PX): Saw chain round file, dia. 4.0 mm
Type 290 (90SG), 291 (90PX): Saw chain round file, dia. 4.5 mm.
(Fig. 62)
The file should cut only when pushed forwards (arrow). Lift the
file when leading it backwards.
First sharpen the shortest cutter. The length of this cutter is
then the standard for all other cutters of the chain.
New saw teeth must be filed to the exact same shape as the
used teeth, including on their running surfaces.
File depending on chain type (90° or 10° to the guide bar).
(Fig. 63)
A file holder makes file guidance easier. It is marked for the
correct sharpening angle of:
α
= 30°
(keep the marks parallel with the chain when filing, see
illustration) and limits the cut depth to the correct 4/5 of the file
diameter.
(Fig. 64)
After having sharpened the chain, the height of the depth
limiter must be checked by means of a chain gauge. See 10
“Extract from the spare parts list”.
Correct even the smallest excess height with a special flat
file (1). See 10 “Extract from the spare parts list”.
Round off the front of the depth limiter (2).
7-2. Cleaning the inside of the sprocket guard
CAUTION: Before doing any work on the guide bar or
chain, always switch off the engine and pull the plug
cap off the spark plug (see 7‑6 “Replacing the spark plug”).
Always wear protective gloves!
CAUTION: Start the chain saw only after having
assembled it completely and inspected.
(Fig. 65)
Remove the sprocket guard (1) (see 6 “PUTTING INTO
OPERATION” for the correct model) and clean out the interior
with a brush.
Remove the chain (2) and guide bar (3).
NOTE:
Make sure there are no residues or foreign matter remaining in
the oil guide groove (4) or on the chain tensioner (5).
To install the guide bar, saw chain, and sprocket guard, see 6
“PUTTING INTO OPERATION” for the correct model.
NOTE:
The chain brake is a very important safety device and
like any other component subject to normal wear and
tear.
Regular inspection and maintenance are important for
your own safety and must be done by a MAKITA service
center.
SERVICE
7. MAINTENANCE
Summary of Contents for 0088381617420
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