Abstract: A portable electric drill is provided with a keyless slidable jaw chuck having three slidable jaws provided with externally extending teeth mounted within a chuck body having three slideways for the chuck jaws and a traverse nut rotatable on the chuck body having internal threads engaged with the chuck jaws, and a locking shell slidable relative to the traverse nut so as to rotate together relative the chuck body. Teeth, lugs or other projections on the rearward annular face of the shell selectively matingly cooperate with teeth, lugs or similar projections provided on the drill housing so that, when the shell is slid rearwardly towards the drill housing the shell and traverse nut are held against rotation relative the drill housing upon actuation of the drill to rotate the chuck body, the chuck jaws will be automatically extended or retracted, depending upon the drill rotation direction, to chuck or unchuck a drill bit or other accessory inserted therebetween.