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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
encounters a foreign object in the wood. The reaction
of the chain drives the saw straight back toward the
operator causing
loss
of saw control. Pushback fre-
quently occurs when the top of the bar
is
used for
cutting (fig.
14).
To
avoid
pushback
1. Be alert
to
forces or situafions that may cause
material
to pinch the top of the chain.
2.
Do
not cut more than one log at a time.
3.
Do
not twist the saw when withdrawing the bar
from a plunge cut or under buck cut (figures
25 to
27
and 33, pages 13 and 15), 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 fig. 15). The reaction of
the chain pulls the saw forward, causing the operator
to
lose control.
Pull-in frequently occurs when the spike bar 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.
To
avoid pull-in
1.
Always start a cut with the chain rotating at full
speed and the spike bar in contact with the wood.
2.
Pull-in may also be prevented by using plastic
wedges
to
open the kerf or cut.
Cutting techniques
Felling
Felling is cutting down a tree.
Before felling a tree, consider carefully all conditions
which may affect the direction of fall, including:
The intended direction of the fall.
The neutral lean of the tree.
Any unusually heavy limb structure.
Surrounding trees and obstacles.
The wind direction and speed.
WARN1 NG!
Always observe the general condition of the tree.
Look
for decay and rot in the trunk. If it is rotted
inside,
it
could snap and fall toward the operator
while being cut.
Also
look for broken or dead branches which could
vibrate loose and fall on the operator. When felling
on a slope, the operator should stand on the up-hill
side.
When felling in the vicinity of roads, railways and
power lines, etc., take extra precautions (see fig.
16).
Inform the police, utility company or railway
authority before beginning
to cut.
WARN1
NG!
Use extreme caution when cutting small
size
brush
and saplings which may easily catch the chain and
pull you off balance.
11