Proper chainsaw chain tension is almost as important as the sharpness of your chain.
A chain that's too tight won't bite into the wood and it will prematurely wear out your drive sprocket because it puts too much tension on the sprocket itself.
When you think about a chainsaw chain, it's basically an oval. As the engine moves the chain at a high rate of speed, that oval wants to become a circle.
Centrifugal force puts pressure on two parts of saw.......the tip of the bar and the drive sprocket. So, if your chain is too tight it won't take long for physics to damage your saw.
A chain that's too loose is also a dangerous scenario. A loose chain can derail itself from the bar and whip back towards you, possibly cutting your hands or legs.
The proper chain tension is similar to a Goldilocks nursery ryme. You don't want it too tight, but you don't want it too loose. You want it just right.
A properly adjusted chain should hold itself up against the bottom of the bar. You don't want the chain to sag, but you don't want it so tight that it damages your saw as it spins around the bar.
To start with, look at your chain. If you can see the chain sagging down from the bottom of the bar.....it's too loose.
On the other hand, if you tug on the chain and it doesn't easy separate itself from the bar.......it's too tight.
This photo shows a chainsaw chain that is too loose. Notice how it sags away from the bar. A chain in this scenario will easily derail itself from the bar possibly causing injury to yourself.
This photo shows a chain that's too tight. Notice as I pull on the chain there's not much "give" to it.
A chain like this will not bite into the wood and it will prematurely ware out your drive sprocket or the tip of your bar.
Typically, most saws will have two options for chain adjustment. Stihl chainsaws will typically have the adjustment screw between the bar and the dog on the saw.
It faces towards the front of the saw, facing the tip of the bar.
Husqvarna saws on the other hand will typically have the adjustment screw on the outside of the bar cover, between the two bar cover nuts. Both versions are adjusted the same way.
To adjust the chainsaw chain tension, loosen the bar nuts first. Loosening the bar nuts will accomplish two things.
First, it allows the bar to move forward as you adjust the tensioning screw which tightens the chain. Second, it allows the bar to move up and down.
Some chainsaw bars can move up to an inch up and down which drastically changes the tension of your chain.
To properly adjust the tension on a chainsaw chain, you need to adjust the tension as you pull UP on the bar.
Think of it this way, as you cut into a log and push down, it forces your bar up. This causes a slack in the chain.
By adjusting your chain in the "up" position, it eliminates the slack in the chain when you cut because the bar is already in the up position.
It almost takes three hands but it's possible with just two. To start, loosen the bar cover nuts. Then take a hand and pull up on the chainsaw bar.
I like to rest my forearm against the chain brake (hand guard) and use my hand to pull up on the bar. It gives me a good leverage point to easily keep upward tension on the bar.
Next, take a screwdriver or chainsaw tool and adjust the chain so that it doesn't sag, but when pulled it places itself back on the bar.
Once you have the perfect tension and still holding up on the bar, tighten the bar cover nuts which locks the bar into place.
To check the proper chain tension, after you've tightened the bar cover nuts just pull up on the chain and see how much it gives.
It just takes a little practice but once you find the right amount of tension, adjusting the chain is really easy. The photo below shows a properly adjusted chainsaw chain.
I'm not pulling very hard and the chain separates itself from the bar, but once I let go it easily retracts and stays firmly positioned on the bar.
Now that your chain is properly adjusted with the bar in the up position, when you make a downward cut into a log it won't force your bar up and loosen the chain.
If you want to properly tighten a chainsaw chain, remember the following steps.
Loosen the bar nuts so you can easily adjust the chain tension screw.
While pulling up on the tip of the bar, adjust the chain so it doesn't sag and it holds itself to the bottom of the bar. I like to pull on the chain for a reference. It should "give" about a 1/4 inch from the bar without much effort.
Finally, while still holding up on the tip of the bar, tighten the bar nuts.
Proper chainsaw chain tension is safer, it cuts better and it will extend the life of both your chainsaw and your chain.