Today we answer a common question that chainsaw owners ask : How Tight Should A Chainsaw Chain Be? This is an important issue that every chainsaw user should know how to do and understand why. An incorrectly tensioned chain affects both the performance of the chainsaw and your own personal safety. The last thing you want is your chain to come off because you were too lazy to check your chain tension (or didn’t know how).
How Tight Should A Chainsaw Chain Be?
The Importance of Correctly Tensioning your Chainsaw Chain
So, you just bought a brand-new chainsaw to cut down some overgrown branches and do a bit of DIY work around the house. Great, but do you know how to tension the chain? Because without proper chain tension, your chainsaw will perform sub optimally, and it can even result in premature wear of certain components like the chain, guide bar, sprocket, clutch, crankshaft, etc. Unfortunately, there are no formulas or concrete rules on how you should tighten your chainsaw chain. Ask a bunch of professionals how they prefer to tension their chainsaw chains, and you will get different answers from each one of them.
The key thing to takeaway here, is that it all depends on personal preference and the type of work you’re doing. Basically, you have to “feel” the amount of tension in the chain and decide whether it needs to be loosened or tightened. This article isn’t just about teaching you how to tighten the chain on your saw. Our goal is to help you understand the proper amount of tension required in a chainsaw chain, and how it affects the performance of your tool. Which means, sometimes you might even have to loosen your chain because it is too tight. Yes, a chain that is too tight can be dangerous for both you and your chainsaw.
Dangers of Running A Chain with Improper Tension
A loose chain will result in slanted cuts, and it won’t “feed” itself into the wood so you’ll have to force the chainsaw in by bearing down on the guide bar using your own body weight which can cause the bar to bend. Another issue with loose chain is the threat of derailing while spinning around the bar at speeds in excess of 60 feet per second. Being struck by a whip made of sharp steel cutters at that speed is going to hurt… a lot. It can even take off a couple fingers or leave a nasty scar on your face if you aren’t careful.
VIDEO | Tensioning A Chainsaw Chain
On the other hand, chainsaw chains that have too much tension in them are also quite harmful. You see, a chainsaw chain is simply a loop of metal links spinning around an oval shaped guide bar. At extremely high speeds, rotational inertia and centrifugal force come into play. What these forces are trying to do, is turn the oval shaped loop into a circle. And this results in 2 main points of stress on both sides of the bar – one at the back of the drive sprocket, and another at the front of the nose sprocket (or bar tip, if it doesn’t have a nose sprocket).
By tightening the chain too much, you’re putting extreme stress on the drive sprocket and bar nose which will result in premature wear. A chain that is too tight also runs the risk of snapping at any moment, and it will eat its way into the bar rails. Bar oil is going to be consumed at a higher rate, and if the chain is too tight it can also damage the clutch and bearings when you start the chainsaw.
So how to make sure that you have the correct amount of tension for optimal performance and safety? Let’s find out.
How to Tighten Chainsaw Chain | Step-by-Step
The first thing you want to do is let your chainsaw cool down, if you’ve been using it to cut wood. It shouldn’t take more than a couple of minutes. This is because the chain is probably hot from slicing through wood and grinding against the bar, so naturally it is going to be in a slightly expanded state. If you tighten it hot, upon cooling the chain will contract and hug the bar so hard that you’ll have trouble moving it with your hands. If a chain is so tight that you cannot freely move it with your hands, it is unsafe to use. Because such a tight chain will cause the engine to stall at low RPMs, and it will smoke and spark as it struggles to move around the bar. All you’ll end up doing is burning your guide bar and clutch, along with wasting a whole lot of bar oil.
VIDEO | How Tight Should A Chainsaw Chain Be?
Once the chainsaw has been left to cool down for about 3 minutes you need to find a stable, relatively flat platform. Out in the woods, this can be a tree stump or the bed of your pickup truck. In the workshop or garage, you probably have a table and bench vice if you’re a serious lumberjack or DIY enthusiast. For tools, you don’t need anything more than a combination wrench, or scrench. Maybe a little grease gun for the bar sprocket if you’re using a guide bar with a nose sprocket. But that’s about it.
Step 1 :
Place the cooled down chainsaw upon the working surface (tree stump, table, etc.), and locate the chain tension adjustment screw. Normally, the adjustment screw is located in one of two positions – between the guide bar and the inside bucking teeth (inboard), or between the two bar nuts on the side cover (outboard). Most modern chainsaws for homeowners feature side mounted chain adjustment (outboard position), which is a lot more convenient to work with.
Step 2 :
Now that you’ve located the adjustment screw, make sure that you can clearly see the head. If not, take a brush or rag and wipe off all the dirt and grime around the clutch cover. Next, you need to loosen up the two bar nuts on the clutch cover. This will allow you to adjust the chain tension pin. If you don’t loosen the bar nuts beforehand, you will simply destroy the threads on the tensioning pin and might damage the bar as well. Don’t take off the nuts, just loosen them enough such that you are able to move the bar up and down by holding its nose. De-activate the chain brake before moving onto the next step (and make sure the engine is turned off!).
Examples of : Various Types of Chainsaw Chain Tensioners
Step 3 :
This one is really important – before you start messing with the adjustment screw, make sure that you’re holding the bar up by its nose. Why do we do this? To ensure that the chain doesn’t lose tension while you’re cutting wood. Think about it, which side of the bar are you using the most while cutting wood? That’s right, the bottom side. Every guide bar is going to rise up, pivoting around the bar studs as you drive it into a log of wood. And this upward movement will change chain tension.
To compensate for this inevitable play in the guide bar (it will happen no matter how tight your bar nuts are), what you need to do is hold the bar up by its nose while adjusting chain tension. This way, you ensure that the chain tension remains steady throughout a day of work. If you own a 65 or 70cc prosumer saw with a guide bar longer than 28”, this process is even more relevant because longer guide bars are going to have more play in them.
VIDEO | How to Properly Tension Chainsaw Chain
Step 4 :
Take the screwdriver end of your scrench and turn the adjustment screw to increase or decrease chain tension. The way this works is, there is a little guided pin underneath the clutch cover which fits into a designated hole in your guide bar, this is usually right next to the oiler holes. There is a slot on the bar, which is supported by two bar studs or bolts on the powerhead. This slot allows the bar to slide forward and backward when the chain tension adjustment pin moves around. When you move the bar outwards, and away from the powerhead, you are increasing chain tension. When the bar moves inwards, chain tension is decreased.
Turning the adjustment screw CLOCKWISE will INCREASE chain tension, turning it COUNTER-CLOCKWISE will DECREASE chain tension. Make quarter or half-turns on the screw. If the chainsaw is brand – new and you just unpacked it from the box, you will probably a few full turns of the screw to get the proper chain tension. For some quick adjustment on the jobsite, a couple quarter turns should be enough.
Step 5 :
Once the chain is snug enough with the bar that you’re unable to see any light passing through in between the chain and bar rails, it is time to test the tension with your fingers. With your index finger and thumb, give the bottom section of the chain loop a light tug. It should snap right back with ease. Do this with the middle of the chain loop, don’t tug around the nose or clutch cover because the chain will be too tight around those spots.
Another indicator used by people is the three quarters rule. Do you see those little drive links in the chain? The ones that actually fit inside the bar groove. When you tug on the middle of the chain with your fingers, no more than 3/4ths of the drive link should be exposed outside the bar groove. If the drive link is completely detached from the inside rails of the bar, it is a bad sign. It can derail at any moment if you use the chain in this condition.
VIDEO | Watch this 30 Second video from Husqvarna
Some professionals also recommend that you move the chain around the guide bar with your hands to check tension levels. It should feel smooth and won’t require much force if the chain is tensioned properly and well lubricated. A loose chain will simply flop around the bar grooves, and a chain that is too tight will refuse to budge. You shouldn’t be forcing the chain around the bar, instead it should be just tight enough to move freely. And remember – NEVER rotate the chain in reverse, since it can jam the sprocket and you’re at a higher risk of cutting your fingers. Always move the chain such that the pointy ends of the cutters are headed AWAY from the powerhead at the top of the bar, and INTO the powerhead at the bottom of the bar. Wear working gloves for this step if you’re inexperienced with chainsaws.
Step 6 :
Now that the tension has been properly adjusted, it is time to tighten the bar nuts. You must still be holding up the nose of the bar all this time, through the previous steps. Take the wrench side of your scrench and tighten up those guide bar nuts on the clutch cover. Check the bar for any play, there should be little to no play if your chainsaw is relatively new.
How often should you tighten the chain on your chainsaw?
When your chainsaw is brand – new, it has a “break in” period (check your owner’s manual). During this period, you will have to tighten the chain more frequently as opposed to a chain that has been in use for a while. Frictional resistance between the chain links are greater during this time, and all moving parts have to bed in, so it is advised that you don’t run the engine at high RPMs while breaking in the chainsaw (and the chain). Break-in allows irregularities on the friction surfaces to smooth out, so the rivets on the chain links are “seated” properly. Check chain tension after every few cuts, make adjustments when needed. According to STIHL owner manuals, the break in period should last between 5 to 15 gas tank fillings.
Also, remember to slightly loosen the chain after you’re finished cutting wood. This will ensure that the chain doesn’t grip the guide bar too tightly after cooling down, especially important if you adjust chain tension in the middle of work (something a lot of professional loggers do). Another benefit of loosening the chain tension after a work session, is the next time you start your chainsaw it will be easier on the clutch and bearings in the drive sprocket. This will extend chain, guide bar, and sprocket lifespan.
Chainsaw Chain Keeps Coming Loose
If the chain keeps losing tension within minutes of tightening, it is important that you take off the clutch cover and check to see if the guide bar is seated properly on the adjustment pin. It is also worth checking out the threads on the bar studs, since they may be worn out. Worn out threads on the bolts will increase the amount of play in the bar, changing chain tension drastically in the middle of a cut.
VIDEO | Why is Your Chainsaw Chain Always Coming Loose?
And finally, check the chain tensioner pin itself. It slides around inside a tab, make sure that the pin moves away from the powerhead when you turn the screw clockwise, and towards the powerhead when you turn the adjustment screw counter clockwise. If the pin moves in opposite directions or doesn’t move at all, it means the chain tensioner mechanism is broken. You will have to take it to the store and replace the pin or order a new tensioner pin and screw online if you’re a handyman and want to do it yourself.
Chainsaw Chain Tightens On Its Own
This is usually the symptom of a dry bar and chain, so check the oiler holes to make sure they aren’t clogged. If the oiler holes are clean, check the bar oil tank next for debris which could be clocking the flow of oil from the tank to the pump. If the tank is clean, there may be an issue with the oiler pump. Another reason for this issue, is a faulty drive sprocket. Make sure you change the drive sprocket for every 2 chain replacements.