Working Advice - Bosch GNF 20 CA Professional Manual Original

OBJ_BUCH-126-002.book Page 21 Wednesday, February 19, 2014 1:49 PM
To start the power tool, push the On/Off switch 10 forwards.
To lock the On/Off switch 10, press the On/Off switch 10
down at the front until it latches.
To switch off the power tool, release the On/Off switch 10 or,
if it is locked, briefly push down the back of the On/Off switch
10 and then release it.
To save energy, only switch the power tool on when using it.
 Check the diamond cutting discs before use. The dia-
mond cutting disc(s) must be mounted properly and be
able to rotate freely. Carry out a test run for at least one
minute without any load. Do not use diamond cutting
discs that are damaged, out-of-balance, or vibrate.
Damaged diamond cutting discs can rupture and lead to in-
juries.
Reduced starting current
The electronic reduced starting current limits the power con-
sumption when switching the tool on and enables operation
from a 13 ampere fuse.
Constant Electronic Control
Constant electronic control holds the speed constant at no-
load and under load, and ensures uniform working perfor-
mance.
Overload Protection
When overloaded, the motor comes to a stop. Relieve the load
on the machine immediately and allow to cool down for ap-
prox. 30 seconds at the highest no-load speed.
Restarting Protection (GNF 35 CA)
The restarting protection feature prevents uncontrolled re-
starting of the machine after an interruption in the power sup-
ply.
To restart the operation, switch the On/Off switch 10 to the
Off position and start the machine again.
Note: Check the function of the restarting protection feature
regularly by having the mains plug pulled during operation
and plugged in again afterwards.

Working Advice

 Exercise caution when cutting slots in structural walls;
see Section "Information on Structures".
 Do not strain the machine so heavily that it comes to a
standstill.
 Clamp the workpiece if it does not remain stationary
due to its own weight.
 The machine may only be used for dry cutting.
Protect the cutting disc against impact, shock and grease. Do
not subject the cutting disc to lateral pressure.
– Adjust the cutting depth, see section "Pre-selecting the
Cutting Depth". To compensate inaccuracies that occur
when breaking away the fin, the cutting depth must be set
approx. 3 mm deeper than the requested slot depth.
– Place the machine with the chaser rollers 7 on the surface
to be worked. The cutting unit must be in the uppermost
position.
– Switch on the machine.
Bosch Power Tools
– Push the release button 3 upwards to release the cutting
unit. Slowly lower and plunge the cutting unit into the ma-
terial.
– Guide the machine with both handles, applying moderate
feed, suited to the material being worked.
– The machine must always work in an up-grinding motion.
Otherwise, the danger exists of it being pushed uncon-
trolled out of the cut. Guide the machine in the direction of
the working-direction arrow 8.
– The machine can be both pushed or pulled in the cutting di-
rection. Vertical slots can easily be cut by pulling the ma-
chine from top to bottom.
– After finishing the working procedure, swivel the cutting
unit out of the slot with the machine still running, until the
cutting unit engages in the uppermost position.
– Switch the power tool off.
Do not brake coasting diamond cutting discs by applying side-
ward pressure.
 Diamond cutting discs become very hot during opera-
tion; do not touch them until they have cooled down.
Remove the remaining fin of the material with the break-out
tool 22.
Curved cuts are not possible, as the diamond cutting discs
could jam in the material.
When cutting through plate materials, ensure that the materi-
als are firmly backed on a surface or supported.
When breaking through walls, e. g. with a rotary hammer,
most of the chipping-off of the surface material can be avoid-
ed by first cutting in a slot with maximum cutting depth.
For cutting expecially hard material, e. g., concrete with high
pebble content, the diamond cutting disc can overheat and
become damaged as a result. This is clearly indicated by cir-
cular sparking, rotating with the diamond cutting disc.
In this case, interrupt the cutting process and allow the dia-
mond cutting disc to cool by running the machine for a short
time at maximum speed with no load.
Noticeable decreasing work progress and circular sparking
are indications of a diamond cutting disc that has become
dull. Briefly cutting into abrasive material (e. g. lime-sand
brick) can resharpen the disc again.
English | 21
22
3 609 929 C89 | (19.2.14)