Abstract: A precision endodontic file including a threaded base having an endodontic file projecting outwardly therefrom is disclosed. A threaded sleeve threadedly receives the base to facilitate precise longitudinal adjustment of the file relative to the sleeve. The bottom end of the sleeve is utilized as a stop which abuts the tooth to thereby limit the depth of file penetration. The threaded body incorporates at least one lock which is continuously biased to a locking position. The threaded sleeve is provided with one or more slots into which the lock can extend to prevent the threaded body from turning relative to the sleeve once the desired length adjustment has been preset. A plastic, transparent throw away type cap overfits the combination of the file and the sleeve and is imprinted with a plurality of graduations thereon to indicate the distance that the bottom of the file extends from the bottom of the sleeve.