Bosch GDS 18 E Professional User Manual
Page 11
English | 11
Bosch Power Tools
1 609 92A 02X | (28.8.12)
Switching On and Off
– To start the machine, press the On/Off switch 5 and keep
it pressed.
– To switch off the machine, release the On/Off switch 5.
When not using the power tool, switch it off in order to save
energy.
Adjusting the Speed
The speed of the switched on power tool can be variably ad-
justed, depending on how far the On/Off switch 5 is pressed.
Light pressure on the On/Off switch 5 results in a low rotation-
al speed. Further pressure on the switch results in an increase
in speed.
Preselecting the Speed
The required speed can be preselected with the thumbwheel
6 (also while running).
Working Advice
f
Before any work on the machine itself, pull the mains
plug.
f
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 impact. The maximum torque is achieved
after an impact duration of 3–5 seconds. After this duration,
the tightening torque is increased only minimally.
However, the transmission housing heats up noticeably.
Note: The consequences of excessive heating-up are high
wear of all hammer mechanism components and a high re-
quirement of lubricant.
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 impact series are
measured and transferred into a diagram, resulting in the
curve of a torque characteristic. The height of the curve corre-
sponds with the maximum reachable 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 given for metal-to-metal screw applications
with the use of washers. After a relatively short impact du-
ration, the maximum torque is reached (steep characteris-
tic curve). Unnecessary long impact duration only causes
damage to the machine.
– A spring-loaded seat is given for metal-to-metal screw ap-
plications, however with the use of spring washers, disc
springs, studs or screws/nuts with conical seat as well as
when using extensions.
– A soft seat is given for screw applications, e. g., metal on
wood or when using lead washers or fibre washers as back-
ing.
For a spring-loaded seat as well as for a soft seat, the maxi-
mum tightening torque is lower than for a hard seat. Also, a
clearly longer impact duration is required.
Reference Values for Maximum Screw/Bolt Tightening Torques
Calculated from the tensional cross-section; utilization of the yield point 90 % (with friction coefficient μ
total
= 0.12). As a control
measure, always check the tightening torque with a torque wrench.
Tips
Torque rods have shanks with precisely calibrated, reduced
diameters. Thus, they act torque-limiting. A torque rod is
placed between the impact wrench and the bit.
Rule of thumb for the application: Core diameter of the
screw/bolt = effective diameter of the torque rod. The impact
duration is to be determined through practical testing.
The thumbwheel 6 must be set to max.
Property Classes accord-
ing to DIN 267
Standard Screws/Bolts
High-strength Bolts
3.6
4.6
5.6
4.8
6.6
5.8
6.8
6.9
8.8
10.9
12.9
M6
2.71
3.61
4.52
4.8
5.42
6.02
7.22
8.13
9.7
13.6
16.2
M8
6.57
8.7
11
11.6
13.1
14.6
17.5
19.7
23
33
39
M10
13
17.5
22
23
26
29
35
39
47
65
78
M12
22.6
30
37.6
40
45
50
60
67
80
113
135
M14
36
48
60
65
72
79
95
107
130
180
215
M16
55
73
92
98
110
122
147
165
196
275
330
M18
75
101
126
135
151
168
202
227
270
380
450
M20
107
143
178
190
214
238
286
320
385
540
635
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