Bosch 23612 - Manual (Page 11)

-11-
For screwing larger, longer wood screws into
hard material, pre-drilling is the best method.
TIGHTENING TORQUE
The tightening torque depends on the
duration of the impacting/tightening action.
The largest tightening torque is achieved
after approx. 6 to 10 Sec. impacting/
tightening action.
The torque build-up depends on the
following factors:
• Hardness of the bolts/nuts.
• Type of washer (disk washer, spring
washer, seal).
• Hardness of the material to be joined.
• Lubricating effect at the surfaces of the
junction.
This leads to the following application cases:
Hard case: The joining of metal to metal with
a disk washer. The maximum torque is
reached after a relative short impacting/
tightening action.
Medium case: The joining of metal to metal
where spring ring washer, disk spring
washer, stud bolts or bolts/nuts with conical
seats are used.
Soft case: The joining of e.g. metal to wood
or insulation material.
For middle or soft joining cases, the
maximum tightening torque is less as for
hard cases. Therefore, a longer impacting/
tightening action is necessary to arrive at the
maximum tightening torque.
FASTENING WITH SCREWS
This procedure shown in (Fig. 6) will enable
you to fasten materials together with your tool
without stripping, splitting or separating the
material.
First, clamp the pieces together and drill the
first hole 2/3 the diameter of the screw. If the
material is soft, drill only 2/3 the proper
length. If it is hard, drill the entire length.
Second, unclamp the pieces and drill the
second hole the same diameter as the screw
shank in the first or top piece of wood.
Third, if flat head screw is used, countersink
the hole to make the screw flush with the
surface. Then, simply apply even pressure
when driving the screw. The screw shank
clearance hole in the first piece allows the
screw head to pull the pieces tightly together.
RUNNING NUTS AND BOLTS
Variable speed control must be used with
caution for driving nuts and bolts with socket
set attachments. The technique is to start
slowly, increasing speed as the nut or bolt runs
down. Set the nut or bolt snugly by slowing the
tool to a stop. If this procedure is not followed,
the tool will have a tendency to torque or twist
in your hands when the nut or bolt seats.
2. Drill same
diameter as
screw shank.
3. Countersink
same diameter
as screw head.
1. Drill 2/3 diameter and
2/3 of screw length for
soft materials, full
length for hard
materials.
Screw
Apply a slight
even pressure
when driving
screws.
FASTENING
WITH SCREWS
FIG. 6