Maintenance And Inspection - Hitachi WH 8DH Mode D'emploi

speed rotation) and the motor is stopped while
continuously driving in screws, the components of
the electronic circuit parts may overheat and be
damaged.
2. Tightening torque
Refer to Figs. 10, 11 and 12 for the tightening torque
of bolts (according to size), under the conditions
shown in Fig. 13. Please use this example as a
general reference, as tightening torque will vary
according to tightening conditions.
NOTE
If a long striking time is used, screws will be strongly
tightened. This may cause the screw to break, or
may damage the tip of the bit.
kg–cm
M8 × 30
1000
800
High tension bolt
600
400
200
Ordinary bolt
0
0 1
Tightening time: sec
(Steel plate thickness
t = 10 mm)
Fig. 10
Bolt
Nut

MAINTENANCE AND INSPECTION

1. Inspecting the driver bit
Using a broken bit or one with a worn out tip is
dangerous because the bit can slip. Replace it.
2. Inspecting the mounting screws
Regularly inspect all mounting screws and ensure
that they are properly tightened. Should any of the
screws be loose, retighten them immediately. Fail-
ure to do so may result in serious hazard.
3. Maintenance of the motor
The motor unit winding is the very "heart" of the
power tool.
Exercise due care to ensure the winding does not
become damaged and/or wet with oil or water.
kg–cm
1000
800
600
400
200
2 3
Steel plate thickness t
Fig. 13
If the unit is held at an angle to the screw being
tightened, the head of the screw may be damaged,
or the specified torque may not be transmitted to
the screw. Always keep the unit and the screw
being tightened in a straight line.
3. Use a tightening time suitable for the screw
The appropriate torque for a screw differs according
to the material and size of the screw, and the
material being screwed etc., so please use a tight-
ening time suitable for the screw. In particular, if
a long tightening time is used in the case of screws
smaller than M8, there is a danger of the screw
breaking, so please confirm the tightening time and
the tightening torque beforehand.
M10 × 30
High tension bolt
Ordinary bolt
0
0 1 2 3
Tightening time: sec
(Steel plate thickness
t = 10 mm)
Fig. 11
*The following bolt is used.
Ordinary bolt: Strength grade 4.8
High tensile bolt: Strength grade 12.9
(
Explanation of strength grade:
4 — Yield point of bolt: 32 kgf/mm
8 — Pulling strength of bolt: 40 kgf/mm
4. Inspecting the carbon brushes (Fig. 6)
The motor employs carbon brushes which are
consumable parts. Since and excessively worn
carbon brush can result in motor trouble, replace
the carbon brush with new ones when it becomes
worn to or near the "wear limit". In addition, always
keep carbon brushes clean and ensure that they
slide freely whthin the brush holders
NOTE:
When replacing the carbon brush with a new one,
be sure to use the Hitachi Carbon Brush Code No.
999054.
5. Replacing carbon brushes
Take out the carbon brush by first removing the
brush cap and then hooking the protrusion of the
carbon brush with a slotted head screw driver, etc.,
as shown in Fig. 8.
English
kg–cm
M12 × 45
1200
1000
High tension bolt
800
600
Ordinary bolt
400
200
0
0 1 2
Tightening time: sec
(Steel plate thickness
t = 25 mm)
Fig. 12
2
3
)
2
7