Chainsaw chains stretch during normal operation and begin to sag on a saw's guide bar. If a chainsaw chain is allowed to become too loose, it can easily come off the bar during operation and create an unsafe situation for the user.
Chainsaw chain tension should be checked and tightened often. We explain simple steps for how to tension a chainsaw chain below.
Correct Chainsaw Chain Tension
Before explaining the tensioning steps, we should explain what proper chainsaw chain tension looks like.
A properly-tensioned chainsaw chain should still be just a little loose on the chainsaw guide bar, but the chain needs to be tight enough that you can't pull the drive links out of the bar nose.
To determine whether or not your chainsaw's chain tension needs to be adjusted, pull the chain away from the guide bar a little to see if the drive links remain engaged or not.
A loose chainsaw chain will look like the one pictured below when it is pulled away from the guide bar. If the chain's drive links are disengaged from the guide bar when pulled, then it's time to tighten it up.
Chainsaw chains can also be overtightened.
There should be at least a little play in the chain, just not enough for the drive links to leave the guide bar. Tightening a chainsaw chain too tightly risks breaking it during operation.
Steps to Tension a Chainsaw Chain
Even though tensioning a chainsaw chain is easy and takes less than a minute, it's important to do each step carefully and correctly. Forgetting to do something like lift the guide bar nose when tightening it can seriously affect your tool.
Most chainsaws come with "scwrench" (screwdriver/wrench) that matches their side plate nut and tension adjustment screw size.