Tighten the Chainsaw Chain to Run Safely
During normal use, the chainsaw chain can begin to wobble and sag, which can cause the chain to slide off the bar – a very dangerous situation. Follow these simple instructions to tension the chain, which is the first step in servicing your chainsaw.
Check the chain tension every time you use the chainsaw. It should flex slightly when you pull it, but the drive links located under the sharp edges should remain in engagement with the chainsaw bar (the solid metal part around which the chain runs). If during operation you notice that the chain saw loses cutting performance, take steps to sharpen the chain .
There is one tension screw next to the chainsaw bar, which is used to adjust the chain. Turning the screw clockwise will tighten the chain and counterclockwise will loosen it. However, do not overtighten the chain, as this may cause it to break.
Many of the newer cordless chainsaws have a manual chain tension dial located at the base of the bar, making tensioning the chain even easier.
Follow the link below for a complete set of chain tensioning instructions.
How to tension a chainsaw chain “wiki useful Instructables