Hitachi WR 12DM Confirm the tightening torque, Tightening torque, Under impact, Holding the tool

English

2. Cautions on use of the speed control switch

6.

Confirm the tightening torque

This switch has a built-in, electronic circuit which

The following factors contribute to a reduction of

steplessly varies the rotation speed. Consequently,

the tightening torque. So confirm the actual

when the switch trigger is pulled only slightly (low

tightening torque needed by screwing up some

speed rotation) and the motor is stopped while

bolts before the job with a hand torque wrench.

continuously driving in screws, the components of

Factors affecting the tightening torque are as follows.

the electronic circuit parts may overheat and be

(1)

Voltage

damaged.

When the discharge margin is reached, voltage

3.

Tightening torque

decreases and tightening torque is lowered.

Refer to Fig. 16 and 17 for the tightening torque

(2)

Operating time

of bolts (according to size), under the conditions

The tightening torque increases when the operating

shown in Fig. 18. Please use this example as a

time increases. But the tightening torque does not

general reference, as tightening torque will vary

increase above a certain value even if the tool is

according to

tightening conditions.

driven for a long time. (See Fig. 16 and 17)

Tightening torque varies, depending on the battery’s

(3)

Diameter of bolt

charge level. Fig. 19 and 20 shows an example of

The tightening torque differs with the diameter of

the relationship between tightening torque and the

the bolt as shown in Fig. 16 and 17. Generally a

number of tightenings, for WR12DM and WR9DM.

larger diameter bolt requires larger tightening torque.

As shown, tightening torque gradually weakens with

(4)

Tightening conditions

the increase in the number of tightenings. In

The tightening torque differs according to the torque

particular, as the torque decreases very close to the

ratio; class, and length of bolts even when bolts

complete discharge (“a” margin in graph), the unit’s

with the same size threads are used. The tightening

impact weakens, the number of time impacts

torque also differs according to the condition of the

declines and tightening torque drops off abruptly.

surface of workpiece through which the bolts are

If this occurs, check torque level, then recharge the

to be tightened. When the bolt and nut turn together,

battery

if necessary.

torque

is greatly

reduced.

4.

Work at a tightening torque suitable for the bolt

(5)

Using optional parts

under impact

The tightening torque is reduced a little when an

The optimum tightening torque for nuts or bolts

extension bar, universal joint or a long socketis

differs with material and size of the nuts or bolts.

used.

An excessively large tightening torque for a small

(6) Clearance of the

socket

bolt may stretch or break the bolt. The tightening

A worn or deformed hex or a square-holed socket

torque increases in proportionate to the operaton

will not give an adequate tightness to the fitting

time. Use the correct operating time for the bolt.

between the nut or anvil, consequently resulting in

5.

Holding the tool

loss of

tightening torque.

Hold the impact wrench firmly with both hands. In

Using an improper socket which does not match

this case hold the wrench in line with the bolt.

to the bolt will result in an insufficient tightening

It is not necessary to push the wrench very hard.

torque. Matching socket and bolt sizes are shown

Hold the wrench with a force just sufficient to

in Table 1, 2, 3

and 4.

counteract the impact

force.

<For WR12DM>

kgf•cm

N•m

M14 ⋅ 50

1600

160

kgf•cm

N•m

M12 ⋅ 45

140

1400

140

1400

120

torqueTightening

kgf•cm N•m

torqueTightening

1200

120

torqueTightening

1200

M10 ⋅

30

1000

100

High tension bolt

1000

100

1000

100

High tension bolt

800

80

800

80

800

80

60

High tension bolt

600

60

600

60

600

Or

dinary bolt

Or

dinary bolt

400

40

Ordinary bolt

400

40

400

40

200

20

200

20

200

20

0

0

0

0

0

0

0

1

2

3

0

1

2

3

0

1

2

3

Tightening

time: sec

Tightening

time: sec

Tightening time: sec

(Steel plate

thickness

(Steel

plate thickness

(Steel plate

thickness

t = 10 mm)

t = 25 mm)

t = 25 mm)

Fig. 16

12