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6 Kickback and Other Reactive Forces
6.1 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
6.2 Kickback
6.2.1 Kickback
WARNING
￭ When this occurs, the energy driving the chain can create
a force that moves the chain saw in a direction opposite to
the chain movement at the point where the 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 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 chain speed, the
speed at which the bar and chain contact the object, the
6 Kickback and Other Reactive Forces
Kickback may occur when the moving chain near
the upper quadrant of the bar nose contacts a
solid object or is pinched.
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