615444 An apparatus for a chainsaw is disclosed comprising a mount (50), a chain support (36) attached movably to the mount, a chain driver, and an endless cutting chain (34). A chain tensioner urges the chain support (36) to move relative to the mount to tension the chain and a sensor (104) is positioned to sense a position of the chain support (36) relative to the mount (50). The sensor (104) can alert a user if the chain stretches beyond a predetermined threshold.
