Bosch GDR 10.8 - Инструкция по эксплуатации - Страница 17

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Operating Instructions

f

Apply the power tool to the screw/nut only
when it is switched off. 

Rotating tool inserts can

slip off.

The torque depends on the impact duration. The max-
imum achieved torque results from the sum of all indi-
vidual torques achieved through impact. The
maximum torque is achieved after an impact duration
of 6 – 10 seconds. After this duration, the tightening
torque is increased only minimally.

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 Seat

When in a test, the achieved torques in an impact
series are measured and transferred into a diagram,
resulting in the curve of a torque characteristic. The
height of the curve corresponds with the maximum
reachable torque, and the steepness indicates the
duration in which this is achieved.

A torque gradient 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 connec-
tion

The following application cases result accordingly:
•

A 

hard seat

 is given for metal-to-metal screw

applications with the use of washers. After a rela-
tively short impact duration, the maximum torque is
reached (steep characteristic curve). Unnecessary
long impact duration only causes damage to the
machine.

•

A 

spring-loaded seat

 is given for metal-to-metal

screw applications, however with the use of spring
washers, disc springs, studs or screws / nuts with
conical seat as well as when using extensions.

•

A 

soft seat

 is given for screw applications, e. g.,

metal on wood or when using lead washers or fibre
washers as backing.

For a spring-loaded seat as well as for a soft seat, the
maximum tightening torque is lower than for a hard
seat. Also, a clearly longer impact duration is required.

Reference Values for Maximum Screw/Bolt Tightening Torques

Calculated from the tensional cross-section; utilization of the yield point 90 % (with friction coefficient
µ

total

= 0.12). As a control measure, always check the tightening torque with a torque wrench.

Tips

Before screwing larger, longer screws into hard mate-
rials, it is advisable to predrill a pilot hole with the core
diameter of the thread to approx. 

2

/

3

 of the screw

length.

Soft Grip

The gripping surface (soft grip) 

5

 reduces the danger

of slipping and thereby improves the grip on the
machine and the handling.
At the same time, the rubber coating achieves a vibra-
tion-reducing effect.

Maintenance and Service

Maintenance and Cleaning

f

Before any work on the machine (e. g., main-
tenance, tool change, etc.) as well as during
transport and storage, set the rotational
direction switch to the centre position. 

Unin-

tentional actuation of the On/Off switch can lead
to injuries.

f

For safe and proper working, always keep
the machine and ventilation slots clean.

When the battery is no longer operative, please refer
to an authorised after-sales service agent for Bosch
power tools.

Property Classes according to 
DIN 267

Standard Screws/Bolts

High-strength 
Bolts

3.6

4.6

5.6

4.8

6.6

5.8

6.8

6.9

8.8

10.9

12.9

M 6

2.71 3.61 4.52 4.8

5.42 6.02 7.22 8.13 9.7

13.6 16.2

M 8

6.57 8.7

11

11.6 13.1 14.6 17.5 19.7 23

33

39

M  10

13

17.5 22

23

26

29

35

39

47

65

78

M 12

22.6 30

37.6 40

45

50

60

67

80

113

135

OBJ_BUCH-223-002.book  Page 17  Thursday, December 14, 2006  10:15 AM