16 ENGLISH
Sharpen the saw chain when:
— Mealy sawdust is produced when damp wood is
cut;
— The chain penetrates the wood with diculty, even
when heavy pressure is applied;
— The cutting edge is obviously damaged;
— The saw pulls to the left or right in the wood. The
reason for this behaviour is uneven sharpening of
the saw chain, or damage to one side only.
Sharpen the saw chain frequently, but
remove only a little material each time.
Two or three strokes with a le are usually sucient for
routine resharpening. When the saw chain has been
resharpened several times, have it sharpened in a
MAKITA specialist repair shop.
Sharpening criteria:
— All cutter length must be equal. Cutters of diering
length prevent the chain from running smoothly,
and may cause the chain to break.
— Do not sharpen the chain once a minimum cutter
length of 3 mm has been reached. A new chain
must then be tted.
— The chip thickness is determined by the distance
between the depth gauge (round nose) and the
cutting edge.
— The best cutting results are obtained with following
distance between cutting edge and depth gauge.
Chain blade 90PX: 0.5 mm
Chain blade 91PX: 0.65 mm
Chain blade 25AP: 0.65 mm
► Fig.28: 1. Cutting length 2. Distance between
cutting edge and depth gauge 3. Minimum
3 mm
WARNING:
• An excessive distance increases the risk of
kick-back.
— The sharpening angle of 30 ° must be the same
on all cutters. Dierences in angle cause the chain
to run roughly and unevenly, accelerate wear, and
lead to chain breaks.
— The side plate angle of the cutter is determined
by the depth of penetration of the round le. If the
specied le is used properly, the correct side
plate angle is produced automatically.
— Side plate angle for each saw chain are as follows:
Chain blade 90PX: 75 °
Chain blade 91PX: 80 °
Chain blade 25AP: 85 °
► Fig.29: 1. Side plate angle
File and le guiding
— Use a special round le (optional accessory) for
saw chains to sharpen the chain. Normal round
les are not suitable.
— Diameter of the round le for each saw chain is as
follows:
Chain blade 90PX: 4.5 mm
Chain blade 91PX: 4.0 mm
Chain blade 25AP: 4.0 mm
—
The le should only engage the cutter on the forward
stroke. Lift the le o the cutter on the return stroke.
— Sharpen the shortest cutter rst. Then the length
of this shortest cutter becomes the standard for all
other cutters on the saw chain.
► Fig.30
— Guide the le as shown in the gure.
—
The le can be guided more easily if a le holder
(optional accessory) is employed. The le holder has
markings for the correct sharpening angle of 30 ° (align
the markings parallel to the saw chain) and limits the
depth of penetration (to 4/5 of the le diameter).
► Fig.31
— After sharpening the chain, check the height of the
depth gauge using the chain gauge tool (optional
accessory).
► Fig.32
— Remove any projecting material, however small,
with a special at le (optional accessory).
— Round o the front of the depth gauge again.
Cleaning guide bar
► Fig.33
Chips and sawdust will build up in the guide bar groove,
clogging it and impairing oil ow. Always clean out the chips
and sawdust when sharpening or replacing the saw chain.
Cleaning the oil discharge hole
Small dust or particles may be built up in the oil dis-
charge hole during operation.
Small dust or particles built up in the oil discharge hole
may impair the oil discharge ow and cause an insu-
cient lubrication on the whole saw chain.
When a poor chain oil delivery occurs at the top of
guide bar, clean the oil discharge hole as follows.
Remove the battery cartridge from the tool.
Remove the sprocket cover and saw chain from the
tool. (Refer to the section titled " Installing or removing
saw chain ".)
► Fig.34: 1. Slotted screwdriver
Remove the small dust or particles using a slotted
screwdriver with a slender shaft or the like.
Insert the battery cartridge into the tool.
Pull the switch trigger to ow built-up dust or particles
o the oil discharge hole by discharging chain oil.
Remove the battery cartridge from the tool.
Reinstall the sprocket cover and saw chain on the tool.
Replacing the sprocket
► Fig.35: 1. Sprocket 2. Locking ring
Before tting a new saw chain, check the condition of
the sprocket.
CAUTION:
• A worn sprocket will damage a new saw chain.
Have the sprocket replaced in this case. The
sprocket needs to be installed so that it always
faces as shown in the gure.
► Fig.36: 1. Locking ring 2. Sprocket
Always t a new locking ring when replacing the
sprocket.
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