Kickback - Stihl MSA 220.0 T Instruction Manual

English
￭ The powerful forces used to cut wood can be reversed and
work against the operator. If the rotating saw chain is
suddenly and significantly slowed or stopped by contact
with any solid object such as a log or branch, or is
pinched, the reactive forces may occur instantly.
￭ These reactive forces may result in loss of control, which,
in turn, may cause serious or fatal injury.
– An understanding of the causes of these reactive
forces may help you avoid the element of surprise
and loss of control. Surprise contributes to
accidents.
The most common reactive forces are:

– Kickback

– Pull-in
– Pushback
7.2 Kickback
7.2.1 Kickback
WARNING
Kickback may occur when the moving chain near
the upper quadrant of the bar nose contacts a
solid object or is pinched.
20
7 Kickback and Other Reactive Forces
￭ When this occurs, the energy driving the chain can create
a force that moves the chain saw in a direction opposite to
the chain movement at the point where the 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 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 chain speed, the
speed at which the bar and chain contact the object, the
location and angle of contact, the condition of the chain,
and how quickly the chain is slowed or stopped, among
other factors.
– The type of bar and 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:
– § 19.107 of UL 62841 - 4 - 1
– § 5.11 of ANSI/OPEI B175.1
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 25° computer-
derived kickback angle when equipped with certain cutting
attachments; and
0458-007-8601-A