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Doc Green’s Woodturning Site

The Wonderful Chainsaw

A chainsaw is the tool of choice for gathering wood from trees. Unfortunately, a chainsaw is one of the more dangerous woodworking tools and is capable of inflicting a horrific injury in the blink of an eye.  

However, I believe that most chainsaw injuries result from complacency and carelessness on the part of the operator.  When used properly, the bar/chain is stable in the cut and its behavior is fully predictable.  It is cause and effect -- if you do this, it will do that. If you don’t do something stupid, it will not rise up in rebellion against you.  

If you have never used a chainsaw, get some instruction from a qualified individual before you go out on your own.  In just a few minutes, an experienced operator can demonstrate the proper techniques for making various cuts and can guide you through your initial efforts.  Most importantly, that person can watch you work and sound the alarm if you start to do something that could get you into trouble.  

In the following I describe several situations that can easily lead to an accident.  Some are obvious; some are not.  

Reaction forces.  The following diagrams illustrate the reaction force that is exerted on the saw when cutting with the bottom, end, and top of the bar.  Two of these tend to move the bar toward you. Take note.  

You, the operator, must supply the force required to hold the saw stationary while making a cut.  This means that the saw will be either pulling you forward or pushing you back.  When you begin a cut, you must expect this force and be prepared to counteract it.  

Keep your feet on solid ground.  Out in the woods, a layer of dry leaves can be slick, and a layer of wet leaves over the top of wet ground can be slick as well. This fact becomes all the more important if you’re working on a steep slope.  

A kickback is an unexpected and rather violent movement of the saw backwards, toward you.  A lot of people have gotten hurt with kickbacks.  

However, there are only three situations that can produce a kickback. These are (1) cutting on the end of the bar, whether intentionally or not, (2) having the chain get pinched at the top of the bar, and (3) having a chain that is very aggressive grab and lock itself in the wood.  

The third situation, having the chain grab, rarely happens because of the design of the chain.  When it happens while cutting on the bottom of the bar, the saw will first be pulled forward followed by a tendency of the bar to rise.  When it happens while cutting on top of the bar, the saw will be thrust backwards violently and will likely come all the way out of the cut.  

Cutting on the end of the bar.  You may never even consider making a cut on the end of the bar, but you can get the same result if you accidentally let it contact another log or branch while focusing your attention on the piece you intend to cut.  Always be sure the tip of the bar is clear.  

The diagram at right illustrates how you can inadvertently let the end of the bar hit another log. You start the cut with the saw tilted downward.  However, near the end of the cut, you lower the body of the saw just a bit (which may come naturally), and the end of the bar rises and contacts the other log.  And away you go.  

This situation may happen as you are cutting apart the fork of a tree, removing a limb from a trunk, or even working in the wood lot if you try to cut one log that is too close to another.

Two other situations come to mind in which the end of the bar may contact another log or limb:

1. Trees with double trunks.  Some trees have double trunks that will be fairly close together at some points.  Don’t let the tip of the bar contact the one beyond the one you’re cutting.  

2.  Making contact with a hidden limb.  Never stick the bar into a pile of brush or debris where the end of it may not be visible.  If the tip of the bar makes contact with a hidden limb, you can get a kickback in short order.

Cutting on top of the bar. Sometimes it is advantageous to make an upward cut with the top of the bar when cuting a tree into manageable sections or when removing limbs from a trunk.  As you lift the saw to initiate the cut, be sure the end of the bar extends well beyond the piece being cut.  That is, use the section of the bar closest to the body of the saw.  Be ready to counter the force that tends to push the saw back toward you.

If you let the section of the bar doing the cutting move toward the end, and if it reaches the top quadrant of the end, the cut will become very aggressive.  Unless you stop the cut immediately, the bar is likely to move toward you because of the increased reaction force, and a kickback is almost certain to occur.  

Cutting a log that’s unsupported at the cut.  If you make a crosscut into the middle of a log that is supported only on the ends, the log will pinch the chain or bar as you near the end of the cut.  If the diameter of the log is greater than the width (top to bottom) of the bar, it will pinch the top of the chain first, and the reaction force will tend to push the chainsaw backwards – another way to get a kickback.  Also, there is a good possibility that you will get the saw stuck in the cut.

The best method for dealing with a situation like this depends a lot on your skill and experience with a chainsaw.  I’m reluctant to make suggestions because an approach that is almost correct can lead to a situation where you almost avoid a kickback.  Call an experienced friend for assistance and swap a combination of beverage and wood for a bit of help in your time of need.

Cutting into a stressed trunk or limb.  Sometimes a falling tree will catch a smaller one, bend it over, and put the trunk of the smaller tree under tremendous stress.  If you cut straight into the stressed area, the trunk will usually split when the cut is only part way through, and the part that splits off will kick like an army mule.  Limbs can also be under stress and may split unexpectedly.  Keep in mind that if it’s bent, it’s under stress and it may have a surprise for you.  

There are a couple of ways to deal with this situation.  The best is to relieve the stress if you can cut away whatever is trapping the smaller tree, and do it safely.  

Another is to make the cut from the side rather than straight on, and be prepared for the kick.  Angle the bar of the saw so that the part that kicks tends to move up and away from the bar.  Make the cut as high on the trunk as you can do so comfortably.

What I’ve done many times is to put the chainsaw down and, standing well to the side, hit the stressed trunk with a sharp axe. Most of the time, one good lick from a level swing will cause the split to occur, which relieves the stress.  My thinking is that I can control the axe much easier than the saw.  

The bouncing bar.  If you touch a small-diameter branch toward the end of the bar with a slow-running chain, the bar will bounce.  And it may bounce sideways and into your foot, if you happen to be holding the branch with your foot.  

And now, a definition: What is a log?  To most people a log is a long section of a tree trunk whose length is many times greater than its diameter.  Woodturners, however, use the term to refer to a section whose length may be only slightly greater than the diameter because that is the typical length used for the preparation of blanks for bowls and other turned items.  Such a short section probably should be called a flitch, but nobody uses that term.  

Therefore, in this article, a log is a short section of a tree trunk just a bit longer that its diameter.

Not a good way to split a log.   Suppose you want to split a log in half lengthwise and the length of the section is a bit longer than the bar on your saw.  You decide to split one end, turn the log around, and then split the other end.  The following diagram shows how you can get into trouble doing it this way.

If you let the end of the bar make contact with the nearly vertical edge of the cut, the bar will tend to climb upward and fly out of the log at high speed.  The situation is made worse by having the saw tilted downward because it tends to gain traction as it climbs out of the cut.

This situation is extremely dangerous because you will not see the hazard developing.  You will be leaning over the saw, cutting down through the log, making good progress.  Then in a flash and with no warning, the bar and chain, running at full speed, will hit you in the face.  Instant lobotomy.

There’s a better way.  Rather than cutting down into one end and then the other, start the cut at the far end of the log with the bar at about a 45 degree angle, and then pull the cut toward you for the full length of the log.  Then, if necessary, roll the log over and do it again to separate the two halves.  

A dangerous business is cutting trees and limbing them up, whether you’re in the woods harvesting turning blanks or simply clearing a storm-blown tree off your driveway.  However, the chainsaw itself does not have to add significantly to the risk. Kickbacks are caused by only two different things:  cutting on the end of the bar and letting the chain get pinched on top of the bar. If you avoid these situations, the chainsaw will be your friend.  

This assumes, of course, that you don’t engage in risky operations. For example, don’t get yourself off balance by trying to reach farther with the saw than you should.  Don’t try to make a cut over your head or higher up than what comes natural for you.  Don’t try to operate the saw when you’re entangled in a bunch of limbs and brush.  And most of all, watch where you stick the bar.  If you apply it to your shoe, it will cut it.  

Christmas vacation, 1958, in northeast Tennessee.   At age 14 I found myself walking up a rather steep hill toward the woods where my Dad and I were going to “cut timber” to provide the lumber to build a new tobacco barn.  I was carrying a freshly sharpened double-bitted axe, the tool of choice for cutting limbs off the trees we would cut with a two-man cross-cut saw.

As we neared the stand of timber where we would be working, my Dad said sternly, without introduction nor elaboration:  “Have some sense when you swing that axe.”  

Funny how some things stick in your mind.  

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