A chainsaw chain should be tight enough to fit snugly against the guide bar but still be able to move freely by hand. Specifically:
- The chain should feel snug but still pull freely around the bar
- When you pull the chain away from the guide bar slightly, the drive links should stay engaged in the bar and not come out
- A common test is to pull the chain on the underside of the guide bar down so one or two drive links come out of the bar rails, then release it. The chain should snap back directly into position
- The top part of the chain in the middle of the guide bar should not lift more than about 5 mm (around 1/4 inch)
- The chain should not be so loose that it sags or risks coming off, as this is unsafe and can cause damage
- Conversely, the chain should not be too tight, as overtightening can cause excessive wear, overheating, and strain on the chainsaw components
In summary, the ideal tension is a balance: the chain fits snugly against the guide bar without sagging, can be pulled around by hand with moderate effort, and the drive links remain engaged in the bar. This ensures safe operation, good cutting performance, and longevity of the chain and bar
