Starting Operation; Working Advice - Bosch GBH 3-28 DRE Professional Manual Original

OBJ_BUCH-770-005.book Page 19 Wednesday, March 23, 2011 2:38 PM
Adjusting the Drilling Depth on the Dust Extraction
Attachment (see figure K)
The required drilling depth X can also be adjusted when the
dust extraction attachment is mounted.
– Insert the SDS-plus drilling tool to the stop into the SDS-
plus tool holder 3. Otherwise, the movability of the SDS-
plus drilling tool can lead to incorrect adjustment of the
drilling depth.
– Loosen the wing bolt 26 on the dust extraction attach-
ment.
– Without switching the power tool on, apply it firmly to the
drilling location. The SDS-plus drilling tool must face
against the surface.
– Position the the guide pipe 27 of the dust extraction at-
tachment in its holding fixture in such a manner that the
head of the dust extraction attachment faces against the
surface to be drilled. Do not slide the guide pipe 27 further
over the telescopic pipe 25 of the dust extraction attach-
ment than required, so that as much as possible of the
scale 25 on the telescopic pipe remains visible.
– Retighten the wing bolt 26 again. Loosen the clamping
screw 23 on the depth stop of the dust extraction attach-
ment.
– Move the depth stop 24 on the telescopic pipe 25 in such
a manner that the clearance X shown in the figure corre-
sponds with the required drilling depth.
– Tighten the clamping screw 23 in this position.
Operation

Starting Operation

Observe correct mains voltage! The voltage of the pow-
er source must agree with the voltage specified on the
nameplate of the machine. Power tools marked with
230 V can also be operated with 220 V.
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.
Position for hammer drilling in concrete or
stone
Position for drilling without impact in wood,
metal, ceramic and plastic as well as for
screwdriving
Bosch Power Tools
Vario-Lock position for adjustment of the
chiselling position
The mode selector switch 9 does not latch in
this position.
Position for chiselling
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.
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 loos-
en the tool insert. When switching the machine on with
the drilling tool jammed, high reaction torques can oc-
cur.

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 19).
– 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.
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