Take a walk through imagination land with me for just a second.
It’s morning. You are standing at your kitchen counter. The “spring” of the toaster releases the delightful aroma of freshly toasted bread. You pick up the butter knife, slide it delicately into the butter when suddenly it flies upward, driving the blunted end of the knife blade deep into your cheekbone!
You fall to the floor, stunned and in pain. How? Why? What?
Crying out to the heavens, you vow that toast will never cross your lips again.
That’s called kickback and it happens with chainsaws too.
See, when a chainsaw chain cuts wood, it’s actually pulling lots of sharp steel through tightly packed wooden fibers. As they pass through, the chain teeth actually “rip” through the wood. It is by the strength and control of your arms that the saw is not pulled from your hands.
And when all those little steel teeth are nice and sharp, they move through the wood like a knife through butter.
Ha! See what I did there with the butter thing?
The sharp tooth bites and cuts through the fibers quickly and with minimal resistance. But the more you use it the duller those teeth become. And when that happens, the teeth bite but they don’t cut…and then you have “kickback”.
KICKBACK or “What the heck just happened?”
Simply put, Kickback is the sudden, quick and often violent re-positioning of the chainsaw cutting bar; resulting in the immediate loss of control over the saw; frequently resulting in grievous bodily injury.
I’m going to go ahead and not display any images of kickback injuries.
If you google it…brace yourself. It ain’t pretty.
How it happens
One cause of kickback is when the tip of the bar (or the “kickback quarter”) comes into contact with the tree, branch, etc while the chain is in motion. As the chain engages the wood, the expectation is for the chain to cut into the material. If insufficient pressure and control of the saw is applied, the chain teeth may bite in the wood, throwing the bar towards the operator.
WARNING: This video has a “pucker factor” of 10.5
Dang. Ok. Let’s talk about what we’ve just seen:
Now this guy looks like he knows what he’s doing. Notice that he’s wearing all the right stuff: helmet with face shield, gloves, work boots, adequate clothing and hearing protection. All good stuff and highly recommended. But when it comes to kickback, none of it saved him from a 20″ bar across the clavicle, did it?
I suspect his shirt and his adrenal glands are shot to hell, but he’s still breathing and he’s not losing copious amounts of fluid so I’d say he got lucky. Really lucky.
As you can see, the speed of a full kickback allows for little to no evasive action. So, here’s the question…Would you have had the reaction time required to avoid what you’ve just witnessed? I wouldn’t have.
It’s like a sucker punch from a shark. You don’t see it coming, but when it happens you can’t help but think “Well, duh! Look at all the teeth, man! Whad’ya think they were for?”
Kickback II- “This time its personal!”
Another form of kickback may occur where the top of the bar is used for cutting or boring and glances off of the wood rather than biting into it or is pinched. In this case the saw may be forced backwards towards the operator, or forced into a position where the tip is pinched and the saw transitions into a classic tip-driven kickback.
Here’s an example of bar tip kickback from Instructor Joe Glenn-
The major difference between the first video and this one is that Instructor Joe has braced the saw against his thigh and is applying considerable strength towards maintaining the saw in anticipation of the kick back. Joe knows the saw will react this way. Even so, the saw threatens to throw itself out of his hands.
Once again, should this occur in the field (or even in your own back yard), there will likely be no anticipation.
NOTE: Bore cutting is a specialized technique requiring proper training, and should not be attempted without such training.
When in doubt, leave it to the professionals.
What to do… What to do?
Over the years, lots of time and development have gone into reducing the changes of Kickback. Here’s a little bit about a lot of stuff.
Low kickback chain features guards fashioned into the cutter links that limit how deep the chain teeth can bite. While it’s not full proof, it has proven to improve safety. There are two commonly noted drawbacks to using a low-kickback chain. The first is that it limits the effective use of the saw when bore cutting. The second drawback to safety chain is that it can be more difficult to sharpen. When compared to the alternative, it doesn’t seem so bad.
The most significant development in anti kickback bar design is the invention of the tip protector.
Tip protectors are metal or plastic devices that fit over the bar tip which hamper the saw in terms of the type and capacity of cuts it can execute.
The chain brake is a steel brake band, wrapped around the driven clutch drum. It is activated by a top-hand guard which is located in front of the forward handle.
Here’s the theory… in the event of a kickback, the operator’s left hand may be violently dislodged from the handle and the top hand guard will be thrown onto his hand, pushing it forward thus engaging the chain brake.
Once engaged, a steel band clamps around the clutch, effectively stopping all chain movement; virtually instantly.
Once again, while not full proof, it does improve the chances of avoiding serious injury.
(See our blog on: What is the Chain Brake?)
Most modern chainsaws require the engagement of two “triggers” to fully operate the saw. When depressed, the throttle trigger controls the speed in which the chain moves. The second trigger (called a stop trigger or “dead mans switch”) must be continually depressed to maintain engine operation. Should the operators hand become dislodged from the saw for any reason, the engine instantly stops. Easily, this is the most effective of the safety measures listed here.
…is anything but common. It never seems to show up when it should. But here’s how we can lure old C.S. to our work area:
- Know your equipment: abilities and limitations. When in doubt, don’t try it. If you’re considering trying something new…take a deep breath, put the saw down and go research it. I’m sure the professionals have something to say about it.
- Take a sobering look at the risks associated. In your mind, become intimately familiar with the worst case scenario. Its easier to avoid something when you know what it looks like.
- Arrogance, ego and an overblown sense of self-confidence will get shredded to nothing in seconds by a wayward chainsaw. Let’s hope that all that gets hit.
- Keep your blade sharp and your wits sharper.
- Respect your saw and it will serve you well. Rest assured, it will let you know the moment you don’t.
Say it once. Say it twice. It’s catchy and its nice-
Chainsaws are dangerous…accidents happen…Be Careful.
Oh yeah, and be careful making toast too.
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