Chain Saw Safety Manual
English
11
WARNING
Reactive Forces including Kickback
WARNING
Reactive forces may occur any time the
chain is rotating. Reactive forces can
cause serious personal injury.
The powerful force used to cut wood can
be reversed and work against the
operator. If the rotating chain is suddenly
stopped by contact with any solid object
such as a log or branch or is pinched, the
reactive forces may occur instantly.
These reactive forces may result in loss
of control, which, in turn, may cause
serious or fatal injury. An understanding
of the causes of these reactive forces
may help you avoid the element of
surprise and loss of control. Sudden
surprise contributes to accidents.
The most common reactive forces are:
– kickback,
– pushback,
– pull-in.
Kickback:
The reaction of the cutting force of the
chain causes a rotational force on the
chain saw in the direction opposite to the
chain movement. This may fling the bar
up and back in a lightning fast reaction in
an uncontrolled arc mainly in the plane
of the bar. Under some cutting
circumstances the bar moves towards
the operator, who may suffer severe or
fatal injury.
Kickback may occur, for example, when
the chain near the upper quadrant of the
bar nose contacts the wood or is
pinched during limbing or when it is
incorrectly used to begin a plunge or
boring cut.
The greater the force of the kickback
reaction, the more difficult it becomes for
the operator to control the saw. Many
factors influence the occurrence and
force of the kickback reaction. These
include chain speed, the speed at which
Some STIHL power tools
are equipped with a cata
-
lytic converter, which is
designed to reduce the
exhaust emissions of the
engine by a chemical
process in the muffler.
Due to this process, the
muffler does not cool
down as rapidly as con
-
ventional mufflers when
the engine returns to idle
or is shut off. To reduce
the risk of fire and burn
injuries when using a cat
-
alytic converter, always
set your power tool down
in the upright position and
never locate it where the
muffler is near dry brush,
grass, wood chips or
other combustible materi
-
als while it is still hot.
Kickback may occur
when the moving saw
chain near the upper
quadrant of the bar nose
contacts a solid object or
is pinched.
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