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7 Kickback and Other Reactive Forces
7.1 Reactive Forces
WARNING
￭ Reactive forces may occur any time the chain is rotating.
Reactive forces can cause serious or fatal personal injury.
￭ The powerful forces used to cut wood can be reversed and
work against the operator. If the rotating saw chain is
suddenly and significantly slowed or 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. Surprise contributes to
accidents.
The most common reactive forces are:
– Kickback
– Pull-in
– Pushback
7.2 Kickback
7.2.1 Kickback
WARNING
￭ When this occurs, the energy driving the saw chain can
create a force that moves the chain saw in a direction
opposite to the saw chain movement at the point where
the saw chain is slowed or stopped. This may fling the bar
up and back in a lightning fast reaction mainly in the plane
of the bar and can cause severe or fatal injury to the
operator.
￭ Kickback may occur, for example, when the saw 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 chain
saw. Many factors influence the occurrence and force of
the kickback reaction. These include saw chain speed, the
speed at which the bar and saw chain contact the object,
7 Kickback and Other Reactive Forces
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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