Bosch Professional GDR 14,4 V-LI Instructions Manual page 23

OBJ_BUCH-832-001.book Page 22 Thursday, October 23, 2008 10:23 AM
22 | English
Working Advice
Apply the power tool to the screw/nut only
when it is switched off. Rotating tool inserts
can slip off.
The torque depends on the impact duration. The
maximum achieved torque results from the sum
of all individual torques achieved through im-
pact. The maximum torque is achieved after an
impact duration of 6–10 seconds. After this du-
ration, the tightening torque is increased only
minimally.
The impact duration is to be determined for
each required tightening torque. The actually
achieved tightening torque is always to be
checked with a torque wrench.
Screw Applications with Hard, Spring-loaded
or Soft Seat
When in a test, the achieved torques in an im-
pact series are measured and transferred into a
diagram, resulting in the curve of a torque char-
acteristic. The height of the curve corresponds
with the maximum reachable torque, and the
steepness indicates the duration in which this is
achieved.
Reference Values for Maximum Screw/Bolt Tightening Torques
Calculated from the tensional cross-section; utilization of the yield point 90 % (with friction coeffi-
cient μ = 0.12). As a control measure, always check the tightening torque with a torque wrench.
total
Property Classes ac- Standard Screws/Bolts
cording to DIN 267
3.6
M 6 2.71
M 8 6.57
M 10
M 12 22.6
M 14
M 16
2 609 140 600 | (23.10.08)
A torque gradient depends on the following fac-
tors:
– Strength properties of the screws/nuts
– Type of backing (washer, disc spring, seal)
– Strength properties of the material being
– Lubrication conditions at the screw/bolt con-
The following application cases result accord-
ingly:
– A hard seat is given for metal-to-metal screw
– A spring-loaded seat is given for metal-to-
– A soft seat is given for screw applications,
For a spring-loaded seat as well as for a soft
seat, the maximum tightening torque is lower
than for a hard seat. Also, a clearly longer im-
pact duration is required.
4.6 5.6 4.8
3.61 4.52 4.8
8.7 11 11.6
13 17.5 22 23
30 37.6 40
36 48 60 65
55 73 92 98
screwed/bolted together
nection
applications with the use of washers. After a
relatively short impact duration, the maxi-
mum torque is reached (steep characteristic
curve). Unnecessary long impact duration
only causes damage to the machine.
metal screw applications, however with the
use of spring washers, disc springs, studs or
screws/nuts with conical seat as well as
when using extensions.
e. g., metal on wood or when using lead
washers or fibre washers as backing.
6.6 5.8 6.8 6.9
5.42 6.02 7.22 8.13
13.1 14.6 17.5 19.7
26 29 35 39
45 50 60 67
72 79 95 107
110 122 147 165
High-strength
Bolts
8.8 10.9 12.9
9.7 13.6 16.2
23 33 39
47 65 78
80 113 135
130 180 215
196 275 330
Bosch Power Tools