Echo CHAIN SAW SAFETY MANUAL - Manual (Page 25)

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Wind bends trees. Gravity bends logs that are not flat on the ground. A log
weakened by a cut over 1/3 the log diameter is like two logs hinged together.
The cut may either close or open wider, depending on how the log is positioned.
In bucking logs, always make the weakening cut from the direction (opposite
the “hinge” side) which causes the cut to widen. If made from the wrong side,
the cut will close, binding the saw and pinching the chain.
If the log is under heavy stress, prevent splitting by making a shallow cut (up
to 1/ 3 dia.) on the “hinge” side first. But, always finish with the final cut in a
direction towards the “hinge” side.
When the log is supported on both ends and is best to be cut in between,
underbuck (cut upward from the bottom side) for the finishing cut.
When you wish to cut off an unsupported section from the end of a log, the
weakening or finishing cut should be an overbuck (from top down). However,
you may begin with a shallow underbuck to avoid splitting.
When the lie is such that the cutoff section will settle, guard against binding
and pinching of the saw between the log sections. This can be done by
inserting a soft wedge into the cut (after the chain is out of the way) to hold
the cut open. In certain cases, the cut may be made on an angle so that it will
widen as the log settles.
HINGE
MOVING OPENED
HINGE
HINGE
PINCHING CLOSED
1ST 1/3 CUT
2ND FINISHING CUT
CUT UP OR
UNDERBUCK
CUT DOWN OR
UNDERBUCK
UNSUPPORTED END
WEDGE
If you’re unsure how a log actually lies, and how it will bend, change its lie. If too heavy to move without strain on the
back muscles, use a lever bar such as a cant hook to move or roll it. NOTE: You may have need to use this procedure
to free the saw, if you misjudged the position of the log.
When a log is flat on the ground, overbuck as far through as possible without cutting into the earth. Then roll the log
over to finish the cut.
MAKE ANGLED CUT WHEN ONE SECTION MAY
SETTLE AGAINST ANOTHER. KEEP BODY OUT OF
BAR/CHAIN PATH!
LOGGER’S HOOK FOR
ROLLING LOGS
PINCHING, BINDING & SPLITTING