Kickback

Kickback may occur when the moving saw chain in or near the upper quadrant of the bar nose is suddenly and significantly slowed or stopped as a result of contact with an object or is pinched.

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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

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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 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 angle of contact, the condition of the 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 chain types are designed to reduce kickback forces. STIHL recommends the use of reduced kickback bars and low kickback chains.

ANSI B 175.1-2000 Chain Saw

Kickback Standard

§5.11 of ANSI standard B 175.1-2000, sets certain performance and design criteria related to chain saw kickback.

To comply with § 5.11 of

ANSI B 175.1-2000:

a)Saws with a displacement of less than 3.8 cubic inches (62 cm³)

–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.

b)Saws with a displacement of 3.8 cubic inches (62 cm³) and above

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–must be equipped with at least one device designed to reduce the risk of kickback injury, such as a chain brake, low kickback chain, reduced kickback bar, etc.

The computer-derived angles for saws below 3.8 cubic inches (62 cm³) displacement are measured by applying a computer program to test results from a kickback test machine.

WARNING

The computer-derived angles of § 5.11 of ANSI B 175.1-2000 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 § 5.11 of ANSI

B175.1-2000 does not automatically mean that in a real life kickback the bar and chain will rotate at most 45°.

WARNING

In order for powerheads below 3.8 cubic inches (62 cm³) displacement to comply with the computed kickback angle requirements of § 5.11 of

ANSI B 175.1-2000 use only the following cutting attachments:

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