Stihl HT Attachment Instruction Manual - Page 11

Reactive Forces WARNING Reactive forces may occur any time the chain is rotating.The force used to cut wood can be reversed and work against the operator. If the rotating chain is suddenly stopped by contact with any solid object such as a branch or is pinched, the reactive forces may occur instantly. These reactive forces may result in loss of control, which, in turn, may cause personal injury. An understanding of the causes of these reactive forces may help you avoid the element of surprise and loss of control. Because of the design of the pole pruner, the reactive forces experienced when working with it are generally not as severe as those encountered with a chain saw. Nevertheless, you should always maintain a proper grip and good footing to control the power tool when you experience such forces. The most common reactive forces are: - kickback, - pushback, - pull-in. Kickback Kickback may occur when the moving saw chain near the upper quadrant of the bar nose contacts a solid object or is pinched. The reaction of the cutting force of the chain causes a rotational force on the pole pruner in the direction opposite to the chain movement. This may cause the bar to move upward. To Avoid Kickback The best protection from kickback is to avoid kickback situations: 1. Be aware of the location of the guide bar nose at all times 2. Never let the nose of the guide bar contact any object. Do not cut limbs with the nose of the guide bar. Be especially careful near wire fences and when cutting small, tough limbs, which may easily catch the chain. 3. Cut only one limb at a time. A = Pull-in 002BA230 KN English a foreign object in the wood. The reaction of the chain pulls the pole pruner forward. Pull-in frequently occurs when the chain is not rotating at full speed before it contacts the wood. To Avoid Pull-in 1. Be alert to forces or situations that may cause material to pinch the chain at the bottom of the bar. 2. Always start a cut with the chain rotating at full speed. B = Pushback B Pushback occurs when the chain on the top of the bar is suddenly stopped when it is pinched, caught or encounters a foreign object in the wood. The reaction of the chain may drive the pole pruner rapidly straight back toward the operator. Pushback frequently occurs when the top of the bar is used for cutting. 001BA038 KN 001BA037 KN A Pull-in occurs when the chain on the bottom of the bar is suddenly stopped when it is pinched, caught or encounters HT 9