An arrangement that provides a semi-automatic tension adjustment of an endless cutting chain on a guide bar of a chain saw as the links of the chain wear with use. A specially designed cam biases a tensioner pin to continuously force the guide bar away from the drive sprocket on the engine chassis to tension the chain. A knob on a clutch cover assembly attached to the engine chassis can be tightened to force two high friction surfaces together to lock the guide bar in a tensioned position, or loosed to release the guide bar to seek a proper tensioned position. An override lever on the face of the clutch cover assembly moves in a channel with peripheral nomenclature that indicates when the cutting chain should be replaced. The entire arrangement is self-contained and does not require any tools to function.
