Through normal use, a chainsaw chain can start to loosen and sag, which can cause the chain to jump off the bar — a very dangerous situation. Follow the easy steps to tighten the chain which is the first step in chainsaw maintenance.
Photo by Dennis van Zuijlekom
Every time you use your chainsaw, check the chain tension. It should have a slight give when you pull it, but the drive links located below the sharp edges should remain engaged with chainsaw bar (the solid metal piece the chain moves around). If you notice during operation that the chainsaw is losing cutting performance then take steps to sharpen the chain.
There is one tension screw located 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. You don't want to over tighten the chain, though, as that could cause the chain to break.
Many of the new cordless chainsaws have a chain tension hand dial located at the base of the bar which makes tightening the chain an even easier task.
Follow the link below for the complete set of instructions for tightening a chainsaw chain.
How to Tighten a Chainsaw Chain [Instructables]