Method Of Operation; Practical Advice - Bosch GSR 12V-15 Professional Manual Original

14 | English
Operation

Method of Operation

The tool holder (1) (with the application tool) is driven by an
electric motor via a gear and impact mechanism.
The working procedure is divided into two phases: Screwing
in and tightening (impact mechanism in action).
The impact mechanism is activated as soon as the screwed
connection runs tight and therefore load is put on the motor.
In this instance, the impact mechanism converts the power
of the motor to steady rotary impacts. When loosening
screws or nuts, the process is reversed.
Start-up
Inserting the Battery
Note: The use of batteries unsuitable for your power tool can
lead to malfunctions or damage to the power tool.
Set the rotational direction switch (7) to the middle position
to avoid unintentionally switching it on. Insert the charged
battery (6) into the handle until you feel it engage and it is
flush with the handle.
Set the Rotational Direction (see figure C)
The rotational direction switch (7) is used to change the ro-
tational direction of the power tool. However, this is not pos-
sible while the on/off switch (8) is being pressed.
Right rotation: To drive in screws and tighten nuts, press
the rotational direction switch (7) through to the left stop.
Left rotation: To loosen and unscrew screws and nuts,
press the rotational direction switch (7) through to the right
stop.
Switching on/off
To start the power tool, press and hold the on/off switch
(8).
The LED (3) lights up when the on/off switch (8) 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 (8).
Adjusting the Speed
You can adjust the speed of the power tool when it is on by
pressing in the on/off switch (8) to varying extents.
Applying light pressure to the on/off switch (8) results in a
low rotational speed. Applying increasing pressure to the
switch increases the speed.
Battery Charge Indicator
When the on/off switch (8) is pressed in halfway or com-
pletely, the battery charge indicator (9) indicates the bat-
tery's state of charge for several seconds. The indicator con-
sists of three green LEDs.
LED
Continuous lighting 3 x green
Continuous lighting 2 x green
Continuous lighting 1 x green
1 609 92A 4JH | (25.10.2018)
Capacity
≥ 66%
33–66%
≤ 33%
LED
Flashing light 1 x green
Temperature-dependent overload protection
In normal conditions of use, the power tool cannot be over-
loaded. If the power tool is overloaded or the permitted bat-
tery temperature is exceeded, the electronics of the power
tool will switch off until the temperature returns to within the
optimum operating temperature range.
Protection against deep discharge
The lithium-ion battery is protected against deep discharge
by the Electronic Cell Protection (ECP). When the battery is
discharged, the power tool is switched off by means of a pro-
tective circuit: The application tool no longer rotates.

Practical advice

Only apply the power tool to the screw/nut when the
u
tool 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. 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 actually achieved tightening torque is
always to 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 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 seat 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 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. Also, a
clearly longer impact duration is required.
Capacity
Reserve
Bosch Power Tools