Method Of Operation; Starting Operation; Practical Advice - Bosch GDS 250-LI Professional Notice Originale

8 | English
Slide the application tool (11) onto the square drive of the
tool holder (1).
Due to the way the system operates, the application tool
(11) will move around slightly in the tool holder (1); this has
no influence on the function/safety.
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 load is therefore put on the motor.
The impact mechanism then converts the power of the mo-
tor to steady rotary impacts. When loosening screws or nuts,
the process is reversed.
Automatic shutdown ABR (ABR = Auto Bolt Release) (see
figure C)
The ABR function automatically shuts down the power tool
when the bolt nut is released. The automatic shutdown pre-
vents the bolt nut from falling down when released. You can
use the "Automatic shutdown (ABR)" button (5) to activate
and deactivate ABR. The LED for "Automatic shutdown
(ABR)" (6) lights up when ABR is activated. The previous
setting is retained when the battery is changed.

Starting Operation

Inserting the Battery
Set the rotational direction switch (7) to the centre position
to protect the power tool against accidental starting.
Push the charged battery (3) into the base of the power tool
from the front until the battery is securely locked.
Set the rotational direction (see figure B)
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).
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 4C1 | (11.10.2018)
The lamp (9) 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.
A light pressure on the on/off switch (8) results in a low rota-
tional speed. Increased pressure on the switch causes an in-
crease 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.
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 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.
Bosch Power Tools