Hitachi WR 12DM Скачать руководство пользователя

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2. Cautions on use of the speed control switch

This switch has a built-in, electronic circuit which
steplessly varies the rotation speed. Consequently,
when the switch trigger is pulled only slightly (low
speed rotation) and the motor is stopped while
continuously driving in screws, the components of
the electronic circuit parts may overheat and be
damaged.

3. Tightening torque

Refer to

Fig. 16

and

for the tightening torque

of bolts (according to size), under the conditions
shown in

Fig. 18

. Please use this example as a

general reference, as tightening torque will vary
according to tightening conditions.
Tightening torque varies, depending on the battery’s
charge level.

Fig. 19

and

shows an example of

the relationship between tightening torque and the
number of tightenings, for WR12DM and WR9DM.
As shown, tightening torque gradually weakens with
the increase in the number of tightenings. In
particular, as the torque decreases very close to the
complete discharge (“a” margin in graph), the unit’s
impact weakens, the number of time impacts
declines and tightening torque drops off abruptly.
If this occurs, check torque level, then recharge the
battery if necessary.

4. Work at a tightening torque suitable for the bolt

under impact

The optimum tightening torque for nuts or bolts
differs with material and size of the nuts or bolts.
An excessively large tightening torque for a small
bolt may stretch or break the bolt. The tightening
torque increases in proportionate to the operaton
time. Use the correct operating time for the bolt.

5. Holding the tool

Hold the impact wrench firmly with both hands. In
this case hold the wrench in line with the bolt.
It is not necessary to push the wrench very hard.
Hold the wrench with a force just sufficient to
counteract the impact force.

6. Confirm the tightening torque

The following factors contribute to a reduction of
the tightening torque. So confirm the actual
tightening torque needed by screwing up some
bolts before the job with a hand torque wrench.
Factors affecting the tightening torque are as follows.

(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. 16

and

)

(3) Diameter of bolt

The tightening torque differs with the diameter of
the bolt as shown in

Fig. 16

and

. 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 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 socketis
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, 2, 3

and

Tightening time: sec

(Steel plate thickness
t = 10 mm)

Tightening time: sec

(Steel plate thickness
t = 25 mm)

Tightening time: sec

(Steel plate thickness
t = 25 mm)

Tightening torque

M10

kgf•cm

1000