A. Correct hinge length - 80% of D.B.H.
B. Correct hinge thickness - 10% of D.B.H.
C. Level back-cut.
To fell trees accurately and safely, you need to know how to do a bore cut, sometimes known as a plunge cut. On trees with forward lean, the traditional “race to the hinge” backcut will sooner or later result in an explosive “barber chair,” in which the tree splits at the base, kicking backwards and falling in an uncontrolled manner. On trees leaning backwards or in other undesirable directions, a bore cut allows you to use wedges to control the direction of its fall.
When you make a bore cut, a strap of wood at the back of the tree holds it safely and securely, allowing you all the time you need to make the hinge exactly the way you want it.
People are often reluctant to use the bore cut because they think it leads to kickback. Your saw won’t kickback if you lead with the bottom of the bar tip, instead of the top. Practice a few, and you’ll get comfortable with it.
The next time you fell a tree, leave a stump 2 to 3 feet high on which to practice bore cuts. Hold the saw to make a horizontal cut, and use your thumb on the throttle, instead of your index finger. It’s more comfortable for horizontal cuts. Imagine where you would want your hinge to be. Hold the saw so the bar is perpendicular to the back of the hinge, and begin to cut into the stump using the bottom half of the tip. When the bar tip is fully covered by wood, rotate the saw with the tip as the pivot until the saw is parallel to the back side of your hinge. Make the bore cut well back of the hinge until you have cut all the way through the tree. Then carefully cut towards the hinge until it is the correct size; the hinge length should be about 80 percent of the tree’s diameter at breast height (D.B.H.), the hinge thickness should be about 10 percent of the tree’s D.B.H. When you are happy with the hinge, cut in the other direction, away from the hinge, leaving a strap of wood at the back that will hold the tree safely on its stump. Cutting through the strap from the outside is quick and easy. You can be safely away from the tree when it falls.