It is very common to see people doing an angled back cut when they hinge cut trees for whitetail deer habitat. This is an improper and unsafe way to cut a tree whether you are cutting by conventional methods to fell a tree by using a face cut and back cut, or hinge cutting for deer habitat.
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Novice inexperienced tree fellers believe that by angling the back cut they will keep the tree from falling over backwards. In fact, a tree is more likely to fall backwards with an angled cut because the cut creates an angled lever that will break the tree across the grain of the wood. If the cutter goes too far or the tree is more fragile and weak than he thought, when the tree breaks it will fall forward off the stump, displacing the top of the tree and causing it to fall backwards.
In contrast, if a feller cuts too far through with a flat cut, and the tree leans back, a lever is created that pulls up along the grain of the wood. It requires only a tiny amount of holding wood to keep a tree from falling over backwards with a flat back cut. Think about how easy it is to break a half inch diameter branch across the grain and how are it is to break a 1/4 inch branch by pulling on the ends. That is the difference between an angled back cut and a flat back cut.
Not only that, but it requires more than twice as much work by the cutter and the saw to make an angled back cut as it does a flat back cut.
In this video,I demonstrate with a handsaw that it takes more than twice as many strokes to make the cut angled at 45 degrees as it does flat, and the resulting hinge is much weaker than the hinge made with a flat cut.
After viewing hundreds of tree disasters on youtube, where trees fall over backwards and land on houses and cars, I believe about 1.3 of those disasters are cause by an angled back cut. Another one third are cause by making the face cut too deep (conventional cutting), and almost all tree fails arise from not leaving enough holding wood in place to keep the tree stable.
Angled back cuts while hinge cutting for deer habitat will result in far more break offs and dead trees than a flat cut, because the flat cut results in a more stable hinge.
Be safe and make sure you always make the cut as flat and horizontal as possible. Safety first while felling a tree. Always wear protective equipment.