Abstract: A drill chuck is disclosed with a pair of jaws and a pair of jaw guiding base plates for centering and holding a drill bit. The chuck comprises a cylindrical housing for the pair of base plates in which the jaws are functionally located. Internal channels and platforms of the above plates guidedly control the movement of the pair of jaws and support a manual adjusting mechanism. The configuration of each of the jaws is such that two rows of triangular spaced apart teeth furnish an adjustable drill receiving opening, or corridor, which is constantly a square for the full range of opening adjustments. Shoulder extensions of the jaws are guidedly located in "V" shaped channels of the base plates. Dowel pins couple an adjusting mechanism to the jaws for guided movement.