Chain tensioner for chain saw

A chain saw comprising:

• a chain saw housing, a drive sprocket mounted to the housing and at least one mounting stud affixed to the housing;
• a guide bar having a peripheral saw chain guide edge mounted to the mounting stud and thereby positioned relative to the drive sprocket for cooperative mounting and guiding of a saw chain loop along a specified guide path extended from the sprocket and along the guide edge of the guide bar, the guide bar as mounted to the mounting stud permitting a limited range of linear sliding movement of the guide bar toward and away from the sprocket;
• an endless saw chain loop having a length that fits the specified guide path within the range of sliding movement of the guide bar;
• a clamping member clamping the bar in a fixed position within said range of movement, and said bar provided with a fixed bearing surface positioned adjacent to and spaced from the mounting stud in the direction of sliding movement, and a cam member having a stud receiving opening receiving said mounting stud and a peripheral outer edge portion of the cam member increasing in distance from the opening, said peripheral outer edge portion adapted to engage the bearing surface, and said cam member rotatable on said mounting stud to vary the point of contact as between the peripheral outer edge portion and the bearing surface to produce sliding movement of the bar within said range of movement and thereby a desired tension of the saw chain loop.