--- 22 ---
(1) Voltage of battery
Tightening torque is affected by the voltage output of the battery. For example, the relationship between
tightening torque and the number of M12 x 45 mm (15/32" x 1-3/4") high-strength bolts tightened is shown in
Fig. 8 below. As can be seen in the graph, tightening torque decreases as the number of bolts tightened
increases. This phenomenon is caused by the decline in voltage output of the battery due to the increasing
number of bolts tightened. In particular, the tightening torque decreases rapidly just before the battery is fully
discharged (range "a" in the graph). As this phenomenon is an inherent drawback in any cordless impact
driver, salespersons are requested to ensure that the customer is fully aware of and understands this
characteristic.
Model WR 8DH
Fig. 8
(2) Effects of low ambient temperatures
The tightening torque required may be reduced at low ambient temperatures or under the influence of grease
and different torque coefficients (dependent on manufacturing and finishing processes, and specified by bolt
manufacturers).
(3) Different bolt diameter
Differences in bolt diameter will cause variation of the required levels of tightening torque. Generally speaking,
tightening torque is higher for large bolts.
(4) Different materials being tightened
When a bolt is tightened into a soft material such as aluminum, plastic, wood, etc., the tightening torque is
considerably less than when the bolt is tightened into a hard material such as steel.
(5) Different tightening conditions
The tightening torque may vary in accordance with bolt torque coefficient (dependent on manufacturing
process, and specified by bolt manufactures), bolt grade and bolt length, even though the dimensions of the
bolts are the same. Tightening torque may also vary depending on the surface finishing state of tightening
materials (steel, aluminum, etc.), and materials to be tightened. In addition, if there is seal packing, clearance,
etc., between tightening materials, the tightening torque is decreased.
Fully charged
a
Battery voltage
Tightening torque
M12 x 45 mm (15/32" x 1-3/4") high-strength bolt (tightening time: 3 seconds)
400
(39.2 N
•
m, 29 ft-lbs)
800
(78.4 N
•
m, 58 ft-lbs)
1,200
(117.6 N
•
m, 86 ft-lbs)
0
2
4
6
8
10
20
40
60
80
100
120
Number of screws driven per charge (EB 9B battery)
Tightening torque
Batter
y v
oltage
(pcs.)
(kgf
•
cm)
(V)
Summary of Contents for WH 8DH
Page 35: ... 32 Assembly Diagram for WH 8DH ...
