Bosch GBH 3-28 DRE Professional - Manual (Page 18)

18 | English
1 609 92A 043 | (10.1.13) Bosch Power Tools
Setting the operating mode
The operating mode of the power tool is selected with the
mode selector switch 9.
Note: Change the operating mode only when the machine is
switched off! Otherwise, the machine can be damaged.
– To change the operating mode, push the release button 8
and turn the mode selector switch 9 to the requested posi-
tion until it can be heard to latch.
Reversing the rotational direction
The rotational direction switch 13 is used to reverse the rota-
tional direction of the machine.
 Actuate the rotational direction switch 13 only when
the machine is at a standstill.
Right rotation: Turn the rotational direction switch 13 to
the stop in position
.
Left rotation: Turn the rotational direction switch 13 to
the stop in position
.
Set the direction of rotation for hammer drilling, drilling and
chiselling always to right rotation.
Switching On and Off
– To start the machine, press the On/Off switch 7.
– To switch off the machine, release the On/Off switch 7.
To save energy, only switch the power tool on when using it.
Setting the Speed/Impact Rate
The speed/impact rate of the switched on power tool can be
variably adjusted, depending on how far the On/Off switch 7
is pressed.
Light pressure on the On/Off switch 7 results in low speed/im-
pact rate. Further pressure on the switch increases the
speed/impact rate.
Safety Clutch
 If the tool insert becomes caught or jammed, the drive
to the drill spindle is interrupted. Because of the forces
that occur, always hold the power tool firmly with both
hands and provide for a secure stance.
 If the power tool jams, switch the machine off and loosen
the tool insert. When switching the machine on with the
drilling tool jammed, high reaction torques can occur.
Working Advice
 Before any work on the machine itself, pull the mains
plug.
Changing the Chiselling Position (Vario-Lock)
The chisel can be locked in 36 positions. In this manner, the
optimum working position can be set for each application.
– Insert the chisel into the tool holder.
– Turn the mode selector switch 9 to the “Vario-Lock” posi-
tion (see “Setting the operating mode”, page 18).
– Turn the tool holder to the desired chiselling position.
– Turn the mode selector switch 9 to the “chiselling” posi-
tion. The tool holder is now locked.
– For chiselling, set the rotation direction to right rotation.
Inserting Screwdriver Bits (see figure L)
 Apply the power tool to the screw/nut only when it is
switched off. Rotating tool inserts can slip off.
To work with screwdriver bits, a universal bit holder 28 with
SDS-plus shank (accessory) is required.
– Clean the shank end of the adapter shank and apply a light
coat of grease.
– Insert the universal bit holder with a turning motion into
the tool holder until it automatically locks.
– Check the locking effect by pulling the universal bit holder.
– Insert a screwdriver bit into the universal bit holder. Use
only screwdriver bits that match the screw head.
– Turn the mode selector switch 9 to the “drilling” position.
– To remove the universal bit holder, pull the locking sleeve
5 toward the rear and remove the universal bit holder 28
out of the tool holder.
Maintenance and Service
Maintenance and Cleaning
 Before any work on the machine itself, pull the mains
plug.
 For safe and proper working, always keep the machine
and ventilation slots clean.
 A damaged dust protection cap should be changed im-
mediately. We recommend having this carried out by
an after-sales service.
– Clean the tool holder 3 each time after using.
If the replacement of the supply cord is necessary, this has to
be done by Bosch or an authorized Bosch service agent in or-
der to avoid a safety hazard.
If the machine should fail despite the care taken in manufac-
turing and testing procedures, repair should be carried out by
an after-sales service centre for Bosch power tools.
In all correspondence and spare parts order, please always in-
clude the 10-digit article number given on the type plate of
the machine.
Position for hammer drilling in concrete or
stone
Position for drilling without impact in wood,
metal, ceramic and plastic as well as for
screwdriving
Vario-Lock position for adjustment of the
chiselling position
The mode selector switch 9 does not latch in
this position.
Position for chiselling
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