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15
this duration, the tightening torque increases only minimally.
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 onto 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 characteristic 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
Consequently, the following applies in each case:
– A
hard seat
is used for metal-to-metal screw applications
that use washers. After a relatively short impact duration,
the maximum torque is achieved (steep characteristic
curve). An unnecessarily long impact duration only
causes damage to the machine.
– A
spring-loaded seat
is used for metal-to-metal screw
applications that use 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 used for screw applications of e.g. metal on
wood or screw applications that use lead washers or fibre
washers 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.
Guide values for maximum screw tightening torques
Figures given in Nm; calculated from the tensional cross-section; utilisation 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.
Property classes accord-
ing to DIN 267
Standard screws/bolts
High-strength bolts
3.6
4.6
5.6
5.8
6.8
8.8
10.9
12.9
M6
2.71
3.61
4.52
6.02
7.22
9.7
13.6
16.2
M8
6.57
8.7
11
14.6
17.5
23
33
39
M10
13
17.5
22
29
35
47
65
78
M12
22.6
30
37.6
50
60
80
113
135
M14
36
48
60
79
95
130
180
215
M16
55
73
92
122
147
196
275
330
M18
81
110
135
180
215
290
405
485
M20
115
155
190
255
305
410
580
690
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.
Note:
Ensure that no metal particles enter the power tool.
After working at a low speed for an extended period, you
should operate the power tool at the maximum speed for ap-
proximately three minutes without load to cool it down.
Recommendations for optimal handling of the battery
Protect the battery against moisture and water.
Only store the battery within a temperature range of -20 to
50 °C. Do not leave the battery in your car in the summer, for
example.
A significantly reduced operating time after charging indic-
ates that the battery has deteriorated and must be replaced.
Follow the instructions on correct disposal.
Maintenance and Service
Maintenance and Cleaning
u
Clean the air vents on your power tool regularly.
The
motor’s fan will draw the dust inside the housing and ex-
cessive accumulation of powdered metal may cause elec-
trical hazards.
u
Remove the battery from the power tool before carry-
ing out work on the power tool (e.g. maintenance,
changing tool, etc.). The battery should also be re-
moved for transport and storage.
There is risk of injury
from unintentionally pressing the on/off switch.
u
To ensure safe and efficient operation, always keep
the power tool and the ventilation slots clean.
After-Sales Service and Application Service
Our after-sales service responds to your questions concern-
ing maintenance and repair of your product as well as spare
parts. You can find explosion drawings and information on
spare parts at:
www.bosch-pt.com
The Bosch product use advice team will be happy to help you
with any questions about our products and their accessor-
ies.
In all correspondence and spare parts orders, please always
include the 10‑digit article number given on the nameplate
of the product.
Bosch Power Tools
1 609 92A 4VZ | (13.10.2020)