Carefulness costs you nothing. Carelessness may cost you your life.
This technique will work every time and it is easy to explain to new workers. It uses gravity to position the bar.
Turn the chainsaw upside down. Loosen the side cover nuts. Turn the chain tensioner screw clockwise to tighten the chain.
Tighten the chain until the bottom edge of the drive link touches the edge of the bar rail and then turn 1/4 turn beyond that. Retighten the side cover nuts and flip the saw back over.
Tightening Your Chainsaw
Phillip Kelley, lead instructor and operations manager of North American Training Solutions demonstrates this chain tightening technique.