Bosch GDR 10,8-LI Professional - Manual (Page 15)

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Bosch Power Tools 1 609 92A 0BV | (18.6.13)
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 corre-
sponds with the maximum reachable torque, and the steep-
ness 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 connection
The following application cases result accordingly:
– A hard seat is given for metal-to-metal screw applications
with the use of washers. After a relatively short impact du-
ration, the maximum torque is reached (steep characteris-
tic curve). Unnecessary long impact duration only causes
damage to the machine.
– A spring-loaded seat is given for metal-to-metal screw ap-
plications, 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 back-
ing.
For a spring-loaded seat as well as for a soft seat, the maxi-
mum 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 materials, it is
advisable to predrill a pilot hole with the core diameter of the
thread to approx.
2 /
3
of the screw length.
Maintenance and Service
Maintenance and Cleaning
 Before any work on the machine itself (e. g. mainte-
nance, tool change, etc.) as well as during transport
and storage, remove the battery from the power tool.
There is danger of injury when unintentionally actuating
the On/Off switch.
 For safe and proper working, always keep the machine
and ventilation slots clean.
When the battery is no longer operative, please refer to an au-
thorised after-sales service agent for Bosch power tools.
After-sales Service and Application Service
Our after-sales service responds to your questions concern-
ing maintenance and repair of your product as well as spare
parts. Exploded views and information on spare parts can al-
so be found under:
www.bosch-pt.com
Bosch’s application service team will gladly answer questions
concerning our products and their accessories.
In all correspondence and spare parts order, please always in-
clude the 10-digit article number given on the type plate of
the machine.
Great Britain
Robert Bosch Ltd. (B.S.C.)
P.O. Box 98
Broadwater Park
North Orbital Road
Denham
Uxbridge
UB 9 5HJ
Tel. Service: (0844) 7360109
Fax: (0844) 7360146
E-Mail: [email protected]
Ireland
Origo Ltd.
Unit 23 Magna Drive
Magna Business Park
City West
Dublin 24
Tel. Service: (01) 4666700
Fax: (01) 4666888
Property Classes accord-
ing 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
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