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ted to the tool holder, it may become loose and can no
longer be controlled.
– Slide the application tool (1) onto the square drive of the
tool holder (2).
Operation
Method of Operation
The tool holder (2) (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.
Overloading the motor is impossible because the impact
mechanism disconnects when the rated load is reached.
Starting Operation
Pay attention to the mains voltage. The voltage of the
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power source must match the voltage specified on the
rating plate of the power tool. Power tools marked
with 230 V can also be operated with 220 V.
Products that are only sold in AUS and NZ: Use a resid-
u
ual current device (RCD) with a nominal residual current
of 30 mA or less.
Setting the Rotational Direction (see figure A)
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 (5) is being pressed.
– Right rotation:
Push the rotational direction switch (7) all the
way to the right.
– Left rotation:
Push the rotational direction switch (7) all the
way to the left.
Switching on/off
To start, press the on/off switch (5) and keep it pressed.
To switch off, release the on/off switch (5).
Adjusting the Speed
You can adjust the speed of the power tool when it is on by
pressing in the on/off switch (5) to varying extents.
A light pressure on the on/off switch (5) results in a low rota-
tional speed. Increased pressure on the switch causes an in-
crease in speed.
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
Bosch Power Tools
Preselecting speed
You can preselect the required speed using the speed
preselection thumbwheel (6), even during operation.
Practical advice
Pull the plug out of the socket before carrying out any
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work on the power tool.
Only apply the power tool to the screw/nut when the
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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 3–5 seconds. After this
duration, the tightening torque is increased only minimally.
Instead, the gearbox housing noticeably heats up.
Note: The consequences of excessive heating include in-
creased wear on all parts of the impact mechanism and a
high need for lubricant.
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 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
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 achieved (steep characteristic curve).
An unnecessarily long impact duration only causes dam-
age 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. A much
longer impact duration is also required.
English | 11
1 609 92A 4PT | (26.10.2018)
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