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Pushback:
Pushback occurs when the chain on the top of the bar is
suddenly
stopped
when it is pinched, caught or
encoun-
ters a
foreign object
in the wood. The reaction of the chain
drives the saw straight back toward the operator and may
cause loss of saw control. Pushback frequently occurs
when the
top
of the bar is used for cutting (see ill. 16).
To avoid pushback
Be alert to forces or situations that may cause material
to
pinch the
top
of the chain.
Do not cut more than one log at a time.
Do not twist the saw when withdrawing the bar from
a
plunge cut or underbuck cut (figures
26 to 30 and 34,
16
pages 19, 20 and 22), because the chain can pinch.
Pull-in:
Pull-in
occurs when the chain on
the bottom of the
bar is
suddenly stopped. The
chain on the bottom of the
bar
stops
when it is
pinched,
caught or
encounters a
foreign
object in the wood (see ill. 17).
The reaction of the
chain
pulls the saw forward
and may cause the operator to
lose
control.
Pull-in frequently occurs
when the bumper spike
of
the
saw is not held securely
against the tree or limb and
when
the chain is not rotating
at full speed before it contacts
the
wood.
Warning!
Use
extreme caution when cutting small size
brush
and
saplings
which may easily catch the
chain and pull you
off
balance.
To avoid pull-in
Always start a cut with the
chain rotating at full
speed
and the bumper
spike in contact with the
wood.
Pull-in may
also be
prevented by using
wedges to
open
the kerf or cut.
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