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9
In order to keep control of your saw, always maintain
a firm foothold. Never work
on
a ladder, in a tree or on
any other insecure support. Never use the saw above
shoulder height (fig.
9).
Position the chain saw in such a way that your body is
clear of the cutting attachment whenever the engine is
running (fig.
10).
Don’t put pressure on the saw when reaching the end
of a cut. The pressure may cause the bar and rotating
chain
to
pop out of the cut or kerf, go out of control and
strike the operator or some other object. If the rotating
chain strikes some other object a reactive force (see
pages
10
to
12
) may cause the chain to strike the
operator.
Reactive forces during the cut, including kickback
WARNING!
Reactive forces, that may occur during any cut are
kickback, pushback and pull-in. Reactive forces
can be dangerous! In any chain saw, 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 like a log or branch
or
is
pinched, the reactive forces instantly occur. These
reactive forces may result in
loss
of control which
may, in turn, cause serious or fatal injury. An
understanding of the causes of these reactive
forces may help you avoid
loss
of control.
The most common reactive forces are
-
kickback,
-
pushback,
-
pull-in.
Kickback:
Kickback occurs when the upper quadrant of the bal
nose contacts a solid object in the wood or is pinched
(fig. 11). The reaction of the cutting force of the chain
causes a rotational force of the chain saw in the direc
tion
opposite
to
the chain movement, mainly in the
plane of the bar. This may flincJ the bar in an uncon-
trolled arc towards the operator.
12
This reaction can occur in a fraction of a second and
under some circumstances, cause the guide bar and
chain
to
strike the operator with enough force to cause
severe or fatal injury.
It
may also occur during limbing.
It
also occurs when the nose ofthe guide bar is pinched
unexpectedly, unintentionally contacts solid material
in the wood (fig.12) or 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.
9