Stihl MSE 250 C Instruction Manual page 13

Kickback may occur
when the moving saw
chain near the upper
quadrant of the bar nose
contacts a solid object or
is pinched.
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.
MSE 250 C
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, the angle of contact,
the condition of the saw chain and other
factors.
The type of bar and saw chain you use
is an important factor in the occurrence
and force of the kickback reaction. Some
STIHL bar and saw chain types are
designed to reduce kickback forces.
STIHL recommends the use of reduced
kickback bars and low kickback chains.
Chain Saw Kickback Standard
The following standards apply with
respect to kickback:
§ 19.108 of UL 60745-2-13
–
§ 5.11 of ANSI/OPEI B175.1-2012
–
These standards, in the following
referred to as "the chain saw kickback
standards" set certain performance and
design criteria related to chain saw
kickback.
To comply with the chain saw kickback
standards, electric chain saws
must, in their original condition,
–
meet a 45° computer derived
kickback angle when equipped with
certain cutting attachments,
and must be equipped with at least
–
two devices to reduce the risk of
kickback injury, such as a chain
brake, low kickback chain, reduced
kickback bar, etc.
The computer derived angles for electric
saws are measured by applying a
computer program to test results from
the kickback test machine.
WARNING
The computer derived angles of the
chain saw standards may bear no
relationship to actual kickback bar
rotation angles that may occur in real life
cutting situations.
In addition, features designed to reduce
kickback injuries may lose some of their
effectiveness when they are no longer in
their original condition, especially if they
have been improperly maintained.
Compliance with the chain saw kickback
standards does not automatically mean
that in a real life kickback the bar and
saw chain will rotate at most 45°.
WARNING
In order for chain saws to comply with
the computed kickback angle
requirements of the chain saw kickback
standards use only the following cutting
attachments:
bar and saw chain combinations
–
listed as complying in the
"Specifications" section of the
instruction manual or
other replacement bar and saw
–
chain combinations marked in
accordance with the standards for
use on the chain saw or
replacement saw chain designated
–
"low kickback saw chain.''
See the section on "Low Kickback Saw
Chain and Reduced Kickback Bars."
English
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