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Switching on "Automatic switch-off" mode (settings 1–
9)
"Automatic switch-off" mode is used for pre-tightening or
tightening screws to prevent the screws from being
tightened too tightly or too loosely.
In "Automatic switch-off" mode, you can preselect a specific
torque (see figure F).
You can switch on "Automatic switch-off" mode as follows:
– "Automatic switch-off" mode is preset on the power tool.
– If the display for torque preselection (22) shows the let-
ter "H", press the button for torque
preselection 1 (+) (23).
Setting 1 for "Automatic switch-off" mode is selected and
is shown on the display for torque preselection (22).
Switching off "Automatic switch-off" mode (setting H)
If "Automatic switch-off" mode is switched off, you cannot
preselect a torque. The power tool reaches a maximum
torque of 300 Nm.
You can switch off "Automatic switch-off" mode as follows:
– If you are at setting 1, press the button for torque
preselection 2 (-) (21).
– If you are at setting 9, press the button for torque
preselection 1 (+) (23).
The letter "H" appears on the display for torque
preselection (22).
Switching "Soft Screwdriving" Mode On and Off
To switch on "soft screwdriving" mode (20), press the but-
tons for torque preselection 1 and 2 ((23)/(21)) at the same
time.
To switch off "soft screwdriving" mode (20), press the but-
tons for torque preselection 1 and 2 ((23)/(21)) at the same
time again.
Selecting the torque level
Select the torque level as follows:
– Select the appropriate torque using the reference values
in the diagram (see figure F).
– Set the correct torque level (1–9).
If the power tool has spring lock washers, activate the
"soft screwdriving" mode.
If the power tool does not have spring lock washers, deac-
tivate the "soft screwdriving" mode.
– Start the screwing process by pressing the on/off
switch (10).
It is recommended to measure the values with a digital
torque spanner.
– For torque values that are 15 % higher than the required
torque, it is recommended to select a lower torque level
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
= 0.12). As a control measure, always check the tightening torque with a torque wrench.
total
1 609 92A 9DD | (27.06.2024)
on the power tool using the torque preselection button
2 (21).
– For torque values that are 15 % below the required
torque, it is recommended to select a higher torque level
on the power tool using the torque preselection button
1 (23).
– For torque values within the limits of 15 %, the selected
torque level can be retained.
Note: It is recommended to carry out the measurements de-
scribed at least three times in order to obtain consistent res-
ults and to be able to save these results in the settings.
Practical advice
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 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 joints
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 with the maximum reachable torque, and the
steepness 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 joint is a metal-to-metal screw application which
uses washers. After a relatively short impact duration, the
maximum torque is reached (steep characteristic curve).
Unnecessary long impact duration only causes damage to
the machine.
– A spring-loaded joint is also a metal-to-metal screw ap-
plication but uses spring washers, disc springs, studs or
screws/nuts with conical joints. It is also called a spring-
loaded joint when extensions are used.
– A soft joint is a screw application of e.g. metal on wood
or a screw application that uses lead washers or fibre
washers as backing.
For a spring-loaded joint as well as for a soft joint, the max-
imum tightening torque is lower than for a hard joint. Also, a
clearly longer impact duration is required.
Bosch Power Tools
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