Chainsaw kick back is a rotational shock resulting from the chain’s cutting tip coming into contact with logs or the guide bar clamping, causing the tool to bounce on or off the user, which can lead to accidents.
There is no way to predict it, but understanding its cause will allow you to take control of the situation using some techniques.
There are several types of chainsaw kickback that lead to loss of control of a chainsaw:
- occurs in cases of bottom sawing, where the chainsaw bar is under the log
- overhead cuts, where the guide bar is over the log
- occurs when the nose or tip of the guide bar contacts branches and tree trunks, kicking the chain saw back toward the user with great force
- occurs while the chain saw is in motion, when the wood closes in, trapping the saw chain in the middle of the cut
When making a straight cut with the top of the cutter bar, additional force is required from the user due to the direction of the chain and tends to push the chainsaw toward the user.
When cutting with the upper and lower cutter bar, the risk of kickback can occur in the cut, jamming the chain, with a sudden change in force to ejection force, which can result in an off-balance and injure the user.
The most uncontrollable chainsaw kickback can occur when cutting tree branches, as the risk of snagging a tree trunk or other object with the tip of the bar increases.
At the edge of the guide bar, the chain teeth rotate around the bar and when they hit a tree trunk or branch, will tend to make a cut, which can cause the bar to quickly bounce upward, guiding the chainsaw toward the user. This can lead to a loss of control of the tool.
Most modern chainsaws include features that reduce chainsaw kickback force, these built-in features include chain brakes, chainsaw bar tip protection. To ensure the effectiveness of these safety features, you need to make sure your chainsaw is properly assembled and that all components are securely fastened and functional.
So when pruning a garden, a smaller bar is often used, this reduces chainsaw kickback and is called a low chainsaw kickback guide bar. The smaller diameter allows for fewer chain teeth, which makes the saw more controllable.
Tip guards help prevent the chain from accidentally dulling and touching the ground or other obstacles and provide easier access to hard-to-reach areas where there may be many obstacles to working safely.
- The Chainsaw Kickback When Starting
- How the Ignition and Chain Brake Work on a Chainsaw
- Useful Video: Chainsaw Kick Back Zone
- Tips for Preventing Chainsaw Kickback Zone
- What causes a chainsaw kickback of the guide bar?
- How do you stop a chainsaw kickback?
- How do you use a chainsaw kickback?
- How dangerous is chainsaw kickback?
The Chainsaw Kickback When Starting
How to start a chainsaw? We try to start the engine of our chainsaw and suddenly we find ourselves in an unpleasant situation. The new and fresh chainsaw will show its good qualities in work, but only after a couple of weeks, it will show chainsaw kickback, having had time to tear a little bit the good-natured owner’s hand.
The kick starter cord when starting the engine with tremendous force returns back, injuring your fingers with the shattering plastic handle.
The occurrence of early ignition on serviceable chainsaws with an electronic high-voltage module is rare, but still it makes itself felt very unpleasantly when starting the chainsaw engine. This problem is not common, but only by owners it is solved sometimes indirectly or immediately – quickly and absolutely radically.
With early ignition, the ignition of the air-fuel mixture during the engine start occurs much earlier than the required moment.
We pull the starter cord with normal effort and hope that the engine will start. But at some point, the starter handle is ripped out of our hands, injuring our fingers, causing a lot of unpredictable emotions and frustration with a very expressive verbal description of what is happening.
Early ignition on a chainsaw engine, can occur when the flywheel with magnets is angled when the flywheel is turned on the shaft when the key is broken, when the engine shaft key groove or hub key groove on the flywheel is broken, when the insert bushing inside the flywheel is turned weakly pressed.
Loss of performance of electronic components in the electronic module circuitry can also contribute to early ignition timing.
Failure to follow the recommendations for the use of spark plugs for this type of electronic module, disregarding the recommendations for the operation of the module itself or installing a defective module from a mass manufacturer.
In the example described, the early ignition torque appeared on a technically sound engine, with a normal flywheel angle and with a functioning electronic ignition module. After a successful start, the saw’s engine ran steadily at medium rpm, but lost a little power and did not pick up enough rpm when trying to increase it.
A similar situation can be simulated on any chainsaw or chainsaw, under conditions similar to this description.
How the Ignition and Chain Brake Work on a Chainsaw
The design of the simplest ignition module installed on chainsaws is technically similar to other, more complex electronic module devices.
Generator coil, control coil and high-voltage transformer – these are the main elements of the electrical circuit of the described device. The generator coil, aka field coil, together with the control coil, which is the pulse coil, are inductively coupled together. In essence, they are both current sources, due to the electromotive force generated in them.
When the motor flywheel rotates, the magnetic field lines of each magnet, passing through the U-shaped magnetic coil, induce in it its directional motion of the magnetic field, hereinafter referred to as magnetic flux, whose value depends on the speed of magnet movement in the magnetic field of the magnetic coil.
Force lines of the magnetic field, located between the magnets, crossing the magnetic coil, change the direction of magnetic flux in the magnetic coil, and the more often the motor flywheel rotates with higher frequency, moving the magnets near the magnetic coil.
The directional magnetic flux generated in the coil of our electronic ignition module penetrates the circuit of two inductively coupled coils located on the same coil. An electromotive force (EMF) is induced in the coils, the polarity of which depends on the direction of the magnetic flux set by the magnetic field of the rotating compound magnet of the flywheel.
At a certain moment of rotation of the flywheel, due to the magnetic flux generated under the influence of the magnetic field of the south pole magnet, a separate EMF is induced in the control and excitation coils with the same sign of polarity. In the control coil the induced current will be directed from point B to point C, and in the excitation coil the current will be directed from point B to point A.
One lead of the control coil circuit, with a negative potential on it at that point in time, is connected to the anode of the control diode, through which only pulses with a positive sign can pass to the control electrode.
The EMF in this coil is present, but the circuit formed by the coil winding with the circuit elements involved will be inactive since no electric current flows through it at that moment in time. There is no control pulse on the control electrode.
One terminal of the excitation coil, with the positive potential on it, is connected to the rectifier diode, which at this moment in time passes the induced current through itself to the capacitor.
A functioning closed circuit of elements is formed – coil→diode→capacitor→primary coil of the high-voltage transformer→common conductor (through point B), through which the electric current flows. That is, during this period of time, the high-voltage capacitor is charged.
Useful Video: Chainsaw Kick Back Zone
In this video, you can see how to prevent kick back zone and how to reduce it.
Tips for Preventing Chainsaw Kickback Zone
Always hold the chain saw firmly with both hands. Your right hand should grip the rear handle firmly and your left hand should grip the auxiliary top handle.
- Before you start cutting or sawing, make sure the work area is clear of obstructions.
- Always watch the tip of the chainsaw guide bar. Do not allow it to come into contact with anything, such as a log, a branch, or any other obstacle.
- Try to work at high engine speeds, at high cutting chain speeds. The chain is most effective at high cutting speeds and is less prone to risk of kickback.
- Always keep the chainsaw at a height no higher than your shoulders and do not cut with the tip of the bar. Use lighter types of tools when cutting branches.
- Stand on your left side when cutting logs, keeping the chainsaw close to you for maximum control.
- Do not operate when you are intoxicated, awake or with back pain.
- Use eye protective equipment, because tiny chips can get caught in the chain and fly in all directions and get in your face.
- Never cut through stacked logs or branches. Always separate them and cut logs and branches one at a time.
- Keep the work area clear of foreign objects.
- Before operating the saw, inspect the tool and make sure the chain brake is in good working order.
If you are ready to work, remember to prevent injuries and wear protective equipment and footwear, hearing and vision protection, and gloves.
What causes a chainsaw kickback of the guide bar?
Kickback can occur when the tip of a chainsaw blade contacts a relatively solid or stationary object when the chain is live. The area of the tip of the rod that is most likely to be involved is known as the “quarter recoil.”
Domestic chainsaws and electric chainsaws have chains that are not much prone to kickback. Their chains have links, with limiters, that keep them from digging into the wood very aggressively. Even if there is a strike when you cut the end, it is not a significant one and even the chain saw guard does not see it.
How do you stop a chainsaw kickback?
There is too much petrol and not enough air in the mix, that’s why the mix is not burnt out completely in the chamber and partially burnt out in the muffler. Exhaust fouling is a clear sign of this. Cleaning the air filter or adjusting the carburetor is necessary.
Kickback also happens if you start cutting at a low kickback chain, the chain just clings to the wood and gets a discount, most often it happens with Chinese-made tools, if you value your health better buy the proven manufacturers (Stihl, Husqvarna).
How do you use a chainsaw kickback?
Spread your legs to control the kickback zone. Hold the saw close to you, this is to reduce the kickback and strain on your back. Change your grip on the chainsaw. Let the rear handle (right hand) rotate freely in your hand.
The only way to avoid chainsaw kickback, in this case, is to stop the chain saw quickly. This is done by a special chain brake (it’s called an ‘inertia brake’) that is actuated by the chainsaw guard in front of the operator’s left hand. It’s a kind of lever that can take up to two positions.
Before the chainsaw is started, the faceplate switches to the ‘closer to hand’ position and thereby ‘cocked’. The operator’s hand rests against it when the kickback occurs and the guard engages, thereby instantly applying the chain brake of the chainsaw. In addition, it can change position without interacting with the operator’s hand, just by virtue of its inertia.
How dangerous is chainsaw kickback?
Kickback is a common problem of chain saw that often strikes even experienced users. For this reason, it is so important to always work only when using the proper safety kit. Keep in mind that the kickback zone speed is very high and a person cannot physically react to such a turn of events even on reflexes.
Therefore, the saw must be mounted so that the blade cannot hit the operator even in the event of kickback. It is forbidden to place the chain saw at shoulder level or higher.
Often, kickback occurs with inexperienced operators. This is caused by insecurely securing the saw in the hand. It also happens when you start sawing with the tip of the bar in the middle part of the wood. In this case, it is necessary to fix the handle of the saw more firmly than when sawing the middle part of the bar of the chain saw.
In fact, what’s the problem to avoid chainsaw kickback? If you follow the elementary rules of chain saw use, this phenomenon rarely occurs.
First of all, your chain saw must be in good condition (without this you should not even start it). You should pay special attention to the tension of the chain and guide bar. If the tension of the chain is weak, the occurrence of a kickback zone is more likely.
Secondly, you must make sure that the far end of the bar does not encounter any obstacles while working. That means you should not cut trees thicker than the width of your chainsaw bar, or cut through several trees in one go.
Also, before you start cutting, make sure that the far end of the bar does not catch any standing (or lying) trees, soil, branches, or large grass. All of these things can get under the chain and jam it in the kerf, causing a kickback zone.
One more moment – it is necessary to begin cutting at medium speed. When the chain has already “seized” the wood and there is a kerf of 3-5 mm depth, saw speed should be increased and till the end of the cut the sawing is done at maximum chain speed.
This, too, reduces the probability of backfire. And the last remark – if you insert the chainsaw into a previously made cut (for example, you sawed half of the trunk, and the chain saw stalled), then the saw bar should be inserted with the flat side (working side), not with the end of the bar forward!
If the earlier cut has closed (under the weight of the tree), it is better to make a new cut side by side than to try to insert the guide bar into the old one with the sharp end forward.
There are also devices that prevent the chainsaw from kicking back. This is already mentioned by the author of the topic, a chain brake. Further, almost all modern gasoline chain saws are equipped with chains with safety contour links of different sizes, which remove layers of wood more evenly, not allowing “sticking”, thereby reducing the chance of backfire and chain jamming.
Other such devices include small-diameter drive sprockets, which reduce the length of the area at the end of the bar that is responsible for the kick.
Use a quality tool and follow the rules of its use. And you won’t have any trouble with any work!