Maintenance And Inspection - Hitachi WR 12DAF Handling Instructions Manual

(1) Voltage
When the discharge margin is reached, voltage
decreases and tightening torque is lowered.
(2) Operating time
The tightening torque increases when the operating
time increases. But the tightening torque does not
increase above a certain value even if the tool is driven
for a long time (See Fig. 15).
(3) Diameter of bolt
The tightening torque differs with the diameter of the
bolt as shown in Fig. 15. Generally a larger diameter
bolt requires larger tightening torque.
(4) Tightening conditions
The tightening torque differs according to the torque
ratio; class, and length of bolts even when bolts with
the same size threads are used. The tightening torque
M8 × 30
kgf cm N m
• •
1000 100
800 80
High tension bolt
600 60
400 40
200 20
Ordinary bolt
0 0
0 1
Tightening time: sec
(Steel plate thickness
t = 10 mm)
Bolt
Nut

MAINTENANCE AND INSPECTION

1. Inspecting the socket
A worn or deformed hex or a square-holed socket will
not give an adequate tightness to the fitting between
the nut or anvil, consequently resulting in loss of
tightening torque. Pay attention to wear of a socket
holes periodically, and replace with a new one if
needed.
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. Failure to do
so may result in serious hazard.
kgf cm N
•
1000
800
600
400
200
0
2 3
Washer
Steel plate thickness t
Washer
also differs according to the condition of the surface
of workpiece through which the bolts are to be
tightened. When the bolt and nut turn together, torque
is greatly reduced.
(5) Using optional parts
The tightening torque is reduced a little when an
extension bar, universal joint or a long socket is used.
(6) Clearance of the socket
A worn or deformed hex or a square-holed socket will
not give an adequate tightness to the fitting between
the nut or anvil, consequently resulting in loss of
tightening torque.
Using an improper socket which does not match to
the bolt will result in an insufficient tightening torque.
Matching socket and bolt sizes are shown in Table 1
and 2.
M10 × 30
m
•
100
High tension bolt
80
60
40
Ordinary bolt
20
0
0 1 2 3
Tightening time: sec
(Steel plate thickness
t = 10 mm)
Fig. 15
*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
Fig. 16
3. Cleaning of the outside
When the impact wrench is stained, wipe with a soft
dry cloth or a cloth moistened with soapy water. Do
not use chloric solvents, gasoline or paint thinner, as
they melt plastics.
4. Storage
Store the impact wrench in a place in which the
temperature is less than 40°C, and out of reach of
children.
5. Service parts list
A: Item No.
B: Code No.
C: No. Used
D: Remarks
English
M12 × 45
kgf cm N m
• •
1200 120
High tension
bolt
1000 100
800 80
600 60
Ordinary bolt
400 40
200 20
0 0
0 1 2
Tightening time: sec
(Steel plate thickness
t = 10 mm)
2
3
)
2
12