Reactive Forces
Reactive Forces including Kickback
WARNING
Reactive forces may occur any time the chain is rotating. Reactive forces can cause serious personal injury.
001BA257 KN
The powerful force 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,
–pushback,
–
WARNING
Kickback:
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.
001BA035 KN
Kickback may occur, for example, when the saw chain near the upper quadrant of the bar nose contacts the wood or is
English
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, 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 Standard
The following standard applies:
–§ 5.11 of ANSI/OPEI
This standard, in the following referred to as ’the chain saw standard’ sets certain performance and design criteria related to chain saw kickback.
To comply with the chain saw standard:
a)Chain saws with a displacement of less than 3.8 cubic inches (62 cm³)
MS 660 | 15 |
