Kickback; Chain Saw Kickback Standards - Stihl MSA 120 C Manual De Instrucciones

7 Kickback and Other Reactive Forces
7.2

Kickback

7.2.1 Kickback
WARNING
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.
￭ 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,
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the location and angle of contact, the condition of the saw
chain, and how quickly the chain is slowed or stopped,
among 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 chain types
are designed to reduce kickback forces.
– STIHL recommends the use of reduced kickback
bars and low kickback chains.
7.2.2

Chain Saw Kickback Standards

The following standards apply with respect to kickback:
– § 19.108 of UL 60745-2-13
– § 5.11 of ANSI/OPEI B175.1
– for Canada: CSA Z62.3
These standards, referred to as "the chain saw kickback
standards" in this chapter, 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 chain saws are
measured by applying a computer program to test results
from a kickback test machine.
WARNING
￭ Compliance with the chain saw kickback standards does
not mean that the bar and saw chain will rotate at most 45°
in a real life kickback. The computer-derived angles of the
chain saw standards may bear no relationship to actual
kickback bar rotation angles that may occur in a real life
cutting situation. Devices designed to reduce the risk of
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