Makita BUC250 Manuel D'instructions page 20

- Make the back cut a little higher than the base cut of
the scarf. The back cut must be exactly horizontal.
Leave approximately 1/10 of the trunk diameter
between the back cut and the scarf.
The wood fibers in the uncut trunk portion act as a
hinge. Do not cut right through the fibers under any cir-
cumstances, as the tree will otherwise fall unchecked.
Insert wedges into the back cut in time. (Fig. 32)
- Only plastic or aluminum wedges may be used to keep
the back cut open. The use of iron wedges is prohib-
ited.
- Stand to the side of the falling tree. Keep an area clear
to the rear of the falling tree up to an angle of 45° either
side of the tree axis (refer to the "felling area" figure
(Fig. 30)). Pay attention to falling branches.
- An escape path should be planned and cleared as nec-
essary before cuts are started. The escape path should
extend back and diagonally to the rear of the expected
line of fall as illustrated in figure. (Fig. 33)
Carrying tool (Fig. 34)
Always remove the battery cartridge from the tool and
overlap the guide bar with the scabbard before carrying
the tool. Also cover the battery cartridge with the battery
cover.
MAINTENANCE
CAUTION:
• Always be sure that the tool is switched off and the bat-
tery cartridge is removed before attempting to perform
inspection or maintenance.
• Always wear gloves when performing any inspection or
maintenance.
• Never use gasoline, benzine, thinner, alcohol or the
like. Discoloration, deformation or cracks may result.
Sharpening the saw chain
CAUTION:
• Always remove the battery cartridge and wear safety
gloves when performing work on the saw chain.
Sharpen the saw chain when:
- Mealy sawdust is produced when damp wood is cut;
- The chain penetrates the wood with difficulty, even
when heavy pressure is applied;
- The cutting edge is obviously damaged;
- The saw pulls to the left or right in the wood. The rea-
son for this behaviour is uneven sharpening of the saw
chain, or damage to one side only. (Fig. 35)
Sharpen the saw chain frequently, but remove only a
little material each time.
Two or three strokes with a file are usually sufficient for
routine resharpening. When the saw chain has been
resharpened several times, have it sharpened in a
MAKITA specialist repair shop.
File and file guiding
- Use a special round file (optional accessory) for saw
chains, with a diameter of 4 mm, to sharpen the chain.
Normal round files are not suitable.
- The file should only engage the material on the forward
stroke. Lift the file off the material on the return stroke.
- Sharpen the shortest cutter first. The length of this cut-
ter is then the gauge dimension for all other cutters on
the saw chain.
- Guide the file as shown in the figure. (Fig. 36)
20
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- The file can be guided more easily if a file holder
Guide the file as shown in the figure. (Fig. 37)
- After sharpening the chain, check the height of the
- Remove any projecting material, however small, with a
- Round off the front of the depth gauge again.
- Wash away dust and particles from saw chain after
Cleaning guide bar (Fig. 38)
Chips and sawdust will build up in the guide bar groove,
clogging it and impairing oil flow. 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 flow and cause an insuffi-
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".)
Remove the small dust or particles using a slotted bit
screwdriver with a slender shaft or the like. (Fig. 39)
Insert the battery cartridge into the tool.
Pull the switch trigger to flow built-up dust or particles off
the oil discharge hole by discharging chain oil. (Fig. 40)
Remove the battery cartridge from the tool.
Reinstall the sprocket cover and saw chain on the tool.
Replacing the sprocket (Fig. 41 & 42)
Before fitting a new saw chain, check the condition of the
sprocket.
• A worn sprocket will damage a new saw chain. Have
Always fit a new locking ring when replacing the
sprocket.
Replacing carbon brushes (Fig. 43 & 44)
Remove and check the carbon brushes regularly.
Replace when they wear down to the limit mark. Keep
the carbon brushes clean and free to slip in the holders.
Both carbon brushes should be replaced at the same
time. Use only identical carbon brushes.
Use a screwdriver to remove the brush holder caps. Take
out the worn carbon brushes, insert the new ones and
secure the brush holder caps.
(accessory) is employed. The file holder has markings
for the correct sharpening angle of 30° (align the mark-
ings parallel to the saw chain) and limits the depth of
penetration (to 4/5 of the file diameter).
depth gauge using the chain gauge tool (optional
accessory).
special flat file (optional accessory).
adjusting the height of depth gauge.
CAUTION:
the sprocket replaced in this case. The sprocket need
to be installed so that it always faces as shown in the
figure.