How to fell a tree
Although the specific technique that professionals use to fell a tree can vary from region to region and even species to species, it generally has three components—THE SCARF, THE BACKCUT, and THE HINGE, as shown in the drawing at far right.
Before making any part of the felling cut, plan ahead for where you want the tree to fall—never into other trees or fallen timber. Also look for obstacles that might block its fall or change its direction, and remove them. "It's a good idea to fell a tree in the direction of its lean, too, if it has any," says Mike Bounds, Director of Product Safety for Poulan chainsaws at the company's Engineering Innovation Center in Texarkana, Arkansas. "But you need to use something to verify how the tree is standing. A tree could look like its leaning because it's on uneven ground, yet be growing straight. To check for lean, take an ax and set it on the ground head down and see how it lines up with the tree."
Next, check your escape route. It should be 45° to the rear of the expected direction of fall. Clear the path of undergrowth, fallen branches, and anything else that could trip you. Then, and only then, determine where the scarf should go, cut it, and remove the resulting triangle-shaped piece of wood.
Finally, do the back cut, making sure you leave a hinge. "The angled cut of the scarf should leave the hinge intact as the tree falls all the way to the ground, providing the most control," notes Bounds. "Cutting less of a scarf to conserve wood in the butt of the tree lessons control and the tree can twist and change direction as it falls. After you've made the back cut, shut off the saw, place it on the ground, and move quickly—but don't run—down your excape rout".
The kickback zone
According to safety experts at Oregon Cutting Systems, a leading manufacturer of saw chains and guidebars, bar-nose kickback ranks as one of the major causes of serious chainsaw injury, and Mike Bounds agrees. "Kickback is the instantaneous reverse reaction that kicks the guide bar up and backward toward the operator when the moving chain at the top tip of the guide bar touches an object, or when the wood closes in and pinches the chain at that spot," he explains.
"A chain brake won't prevent kickback," Bounds continues. "It only stops the chain from moving." Those exper enced with chainsaw operation call the area of the guidebar highlighted in the photo at left the "kickback zone," and avoid making cuts with that portion.
Safety gear suggestions
A chainsaw that reduces fatigue—the factor behind many accidents—has the lightest weight for the amount of engine size needed for the job. It also should feature a system to reduce the amount of vibration delivered to the handles, as well as a reliable chain brake, reduced-kickback guidebar, and low-kickback saw chain.
To guard against injury, the Occupational Safety and Health Administration requires that chainsaw operators employed by logging companies wear:
- Pants or chaps made from chainsaw-resistant material
- Safety glasses or goggles
- Hearing protection (NRR of 23-25 dB)
- Hard hat
For only occasional chainsawing, though, you might not want to go to the expense of chainsaw-resistant chaps, but do plan on wearing the other items. And to those add steel-toed boots or shoes, and non-slip gloves. (Cut-resistant ones are available, and can be combined with forearm-protecting sleeves.) Then, keep on your toes to avoid injury.
Limbing and bucking safely
After the tree hits the ground, look for any probable hazards that it may have created. Dead or broken-off limbs overhead in a nearby tree might fall due to the activity. Small saplings bent to the ground by the fallen tree can spring back when you relieve the pressure through further sawing for limbing and bucking (crosscutting the trunk into manageable log lengths, as shown above).
As shown in the drawings below, a fallen tree has stresses created by its fall. You must be aware of these when limbing and make your chainsaw cuts accordingly. For instance, on a limb sticking straight out from the trunk, you'd make your first cut on the side facing the ground. This relieves compression stress. Your second cut, on top of the limb and slightly offset from the first, relieves tension as it frees the limb. Remember, that the first cut is always on the compression side.
Following limbing comes bucking the trunk. For large-diameter trunks intended for further milling into boards, you must determine the length of the logs you can or want to handle based on any visible defects. That is, a big knot or rotten burl shouldn't end up in the middle of what will eventually become a board. And because the trunk rests directly on the ground, you have to saw through from the top, beginning at the butt (lower end).
"Keep in mind that the most common injury in logging comes from getting hit by a branch or part of the bucked log as it rolls," says Poulan's safety director. "So just as in felling the tree, you must calculate what each piece of wood will do when it is free of the tree. And during the limbing and bucking process, never let the saw chain contact the ground. It travels faster than 50 mph and will immediately dull."
A dozen safety tips
- Never run a chainsaw when tired, after drinking alcohol, or when taking medication.
- Be sure to read the manufacturer's operating and safety instructions.
- Just as when ripping wood on a tablesaw, stand slightly to the side of the chainsaw when limbing and bucking in case it kicks back. Grip the handles firmly, with the right hand on the throttle handle and the left on the front handle, even if left-handed.
- Always run a chainsaw full throttle when cutting.
- Never cut above shoulder height or over-reach to make a cut with a chainsaw.
- Beware when cutting slender shoots and branches. The chain may catch and whip them toward you.
- Unless trained, don't operate a chainsaw in a tree or from a ladder.
- Never hand-hold wood to saw or have someone else hold the wood. It's possible for a chainsaw to "skate" across the wood and into a hand.
- Maintain proper chain tension. A loose chain can come off and strike you.
- Never try to cut with a dull saw chain. (When a chain produces dust rather than chips, it's dull.)
- Carry a chainsaw with the engine off and the guidebar to the rear.
- Don't work in the woods alone. And keep your helper two tree lengths away when felling a tree.