by Tim Ard, Forest Applications Training, Inc.
A tree is down and now the real work begins. We have to cut it into manageable pieces to be able to either move it, chip it, or sell it. In this process are a magnitude of issues that can effect our safety and profit.
Where to cut is formed by our need to move/remove the cut wood pieces. Planning a required length for either hand movement or machine. Sometimes our decision is dictated by market or work area requirements. Firewood length, chip length or environmental concern length are all necessary size requirements. Whatever the size needed, at the point you make the cut, a plan must be developed.
A decision has to be made asking yourself these questions. When I make this cut and sever this piece will it move? Side to side, up and down or back to forward? We must anticipate movement to decide how to control it. We decide where to cut and will it move, then next is what technique to cut the piece. Sometimes just a straight kerf cut to sever the piece. Sometimes a notch and hinge to slow reactions and pinch pressures. Sometimes offset cuts reduce movement and eliminate pinch and bind.
Two very useful techniques are a simple kerf and or a slide notch.
The kerf is the term used to describe a cut made into a log or limb. Making a cut with a saw into the log or limb produces a kerf. The kerf is normally about 3/8” wide. The depth of the kerf is regulated by our depth of cut.
There are really only two types of kerf’s used when working with a saw. A straight kerf and a combination of kerf’s we call a notch and back cut.
A straight kerf will close quickly under pressure and force fibers to bind a saw bar and chain on the compression side of a log or limb. On the tension side of the log or limb a straight kerf will work fine to reduce bind as long as a kerf or notch and hinge on the compression side allows movement without closing or fiber splitting.
The Slide Notch
The slide notch is produced by simply turning the bar and chain parallel to the limb or trunk on the compression side. Now slide the bar up or down the surface making an opening in the bark and the fiber. This shallow slide into the fiber will work as a notch opening, of about 90 degrees. Then as the kerf cut is made from the opposite tension side, the fiber is allowed to work as a hinge. The notch and hinge can even be made toward the side of the piece to direct the limb or trunk in a more sideways direction. In either position the slide notch works much better than a simple kerf cut. A slide notch can be made just as quickly, if not faster, than a straight kerf cut and eliminates the chances of compression side bind.
The notch is used in our work to allow the wood fiber to bend, relieving pressure as the wood piece is severed. Because tree trunks and limbs grow is circles, adding growth rings annually for strength while maintaining flexibility, a notch is necessary to keep the pressures from splitting the fibers as they move in a desired direction. You can illustrate this by just making a kerf into a limb piece and then applying pressure to the limb. The fiber will split off instead of bending in the desired direction. If you make just a small mark (slide notch) on the limb on the opposite side from your kerf, when pressure is applied, the fiber will work as a hinge into that notch opening. This relief notch is reducing the fiber separation and splitting that occurred in the previous.
Operators sometime use notches to try to prevent binding in a limb or log. The notch opening is placed deep into the piece with thoughts to reduce binding on the compression side (the side closing on your saw bar). It’s not the notch however that reduces the pinch it’s the hinge wood just behind the notch that eliminates the pinch. A deeper notch simply moves the pinch point not the pinch.The depth of the notch really only moves the compressing pinch point closer to the middle of the limb or logs diameter. This will actually pinch your guide bar with more pressure than a shallow notch. Several kerf’s will do a better job than a notch to reduce the pinch possibilities in pressure situations. The best however is a hinge (or holding fiber) to keep your guide bar and chain from becoming stuck. It can definitely help the operator read the anticipated movement with less bind possibilities.
SO, next time you plan to clear a storm situation cutting a tree trunk or limb, try a Slide Notch Instead.
Remember, when using a chainsaw an important part of your plan is to read and fully understand the manufacturers operation manual and to always wear proper Personal Protective Equipment when using a chainsaw.
A great way to learn how these techniques work in action is to attend one of our ForestApps Storm Sawing Workshops. Check out our website at ForestApps.com for more details or contact our office at info@ForestApps.com or call 770-543-9862.
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