Maintenance; Replacing Carbon Brushes - Makita 6991D Instruction Manual

MAINTENANCE

1. Limit mark
• If the tool is operated continuously until the battery
cartridge has discharged, allow the tool to rest for 15
minutes before proceeding with a fresh battery.
The fastening torque is affected by a wide variety of factors
including the following. After fastening, always check the
torque with a torque wrench.
1. When the battery cartridge is discharged almost com-
pletely, voltage will drop and the fastening torque will be
reduced.
2. Socket
•
•
3. Bolt
•
•
4. The manner of holding the tool or the material of driving
position to be fastened will affect the torque.
5. Operating the tool at low speed will cause a reduction in
the fastening torque.
CAUTION:
• Always be sure that the tool is switched off and the
battery cartridge is removed before attempting to
perform inspection or maintenance.

Replacing carbon brushes

001145
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 iden-
tical carbon brushes.
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Failure to use the correct size socket will cause a
reduction in the fastening torque.
A worn socket ( wear on the hex end or square end )
will cause a reduction in the fastening torque.
Even though the torque coefficient and the class of
bolt are the same, the proper fastening torque will
differ according to the diameter of bolt.
Even though the diameters of bolts are the same, the
proper fastening torque will differ according to the
torque coefficient, the class of bolt and the bolt
length.
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