Bosch Professional GDR 18 V-LI MF Instructions Manual page 16

16 | English
(10) and release it again before pushing the "Drilling/screw-
driving" selector switch (4) to the required position.
Always push the "Drilling/screwdriving" selector switch (4)
as far as it will go. Operating the power tool with the
"Drilling/screwdriving" selector switch (4) not fully in posi-
tion can damage the power tool.
Position for impact drilling
Position for slow drilling with a large drilling
diameter in wood, metal, ceramic and plastic
Position for rapid drilling with a small drilling
diameter in wood, metal, ceramic and plastic
Switching on/off
To start the power tool, press and hold the on/off switch
(10).
The lamp (3) lights up when the on/off switch (10) is lightly
or fully pressed, meaning that the work area is illuminated in
poor lighting conditions.
To switch off the power tool, release the on/off switch (10).
Adjusting the Speed
You can adjust the speed of the power tool when it is on by
pressing in the on/off switch (10) to varying extents.
A light pressure on the on/off switch (10) results in a low ro-
tational speed. Increased pressure on the switch causes an
increase in speed.
Practical advice
Only apply the power tool to the screw/nut when the
u
tool is switched off. Rotating tool inserts can slip off.
When drilling, do not apply too much pressure to the
u
power tool. Excessive pressure can damage the tip of the
drill bit, compromise the performance and shorten the
service life of the power tool.
Working in especially dusty environments can lead to
u
failure of the power tool. If the power tool suddenly
Guide values for maximum screw tightening torques
Figures given in Nm; calculated from the tensional cross-section; utilization of the yield point: 90% (with friction coefficient
µ = 0.12). As a control measure, always check the tightening torque with a torque wrench.
total
Property classes Standard screws
according to
3.6 4.6
DIN 267
M6 2.71 3.61
M8 6.57 8.7
M10 13 17.5
M12 22.6 30
M14 36 48
Tips
Before screwing larger, longer screws into hard materials, it
is advisable to pre-drill a pilot hole with the core diameter of
the thread to approx. 2/3 of the screw length.
1 609 92A 4AK | (31.08.2018)
fails, remove the carbon brushes and check them (see
section "Replacing the carbon brushes").
The torque depends on the impact duration. The maximum
achieved torque results from the sum of all individual
torques achieved through impact. Maximum torque is
achieved after an impact duration of 6–10 seconds. After
this duration, the tightening torque is increased only minim-
ally.
The impact duration is to be determined for each required
tightening torque. The tightening torque actually achieved
should always be checked with a torque wrench.
Screw applications with hard, spring-loaded or soft seats
When the achieved torques in an impact series are measured
during a test and transferred into a diagram, the result is the
curve of a torque characteristic. The height of the curve cor-
responds to the maximum achievable torque, and the steep-
ness indicates the duration in which this is achieved.
A torque gradient depends on the following factors:
– Strength properties of the screws/nuts
– Type of backing (washer, disc spring, seal)
– Strength properties of the material being screwed/bolted
together
– Lubrication conditions at the screw/bolt connection
The following application cases result accordingly:
– A hard seat is a metal-to-metal screw application which
uses washers. After a relatively short impact duration, the
maximum torque is achieved (steep characteristic curve).
An unnecessarily long impact duration only causes dam-
age to the machine.
– A spring-loaded seat is also a metal-to-metal screw ap-
plication but uses spring washers, disc springs, studs or
screws/nuts with conical seats. It is also called a spring-
loaded seat when extensions are used.
– A soft seat is a screw application of e.g. metal on wood or
a screw application that uses lead washers or fibre wash-
ers as backing.
For a spring-loaded seat, as well as for a soft seat, the max-
imum tightening torque is lower than for a hard seat. A much
longer impact duration is also required.
5.6 4.8 6.6 5.8
4.52 4.8 5.42 6.02
11 11.6 13.1 14.6
22 23 26 29
37.6 40 45 50
60 65 72 79
Belt clip
You can use the belt clip (6) to hang the power tool on a belt,
for example. You then have both hands free and the power
tool is always at hand.
High-strength screws
6.8 6.9 8.8 10.9
7.22 8.13 9.7 13.6
17.5 19.7 23 33
35 39 47 65
60 67 80 113
95 107 130 180
Bosch Power Tools
12.9
16.2
39
78
135
215