Abstract: A tool chuck includes a spindle having a barrel with an axial bore therein, and a collar slidably disposed about the barrel. A diametrical slot within the barrel receives a pair of opposed, pivoting toggles which engage and retain the end of a tool inserted in the barrel bore. The toggles are pivoted by a pair of linking members secured to a cylindrical member disposed in axially translatable fashion in the upper end of the bore. The cylindrical member is translated by the collar by means of an annular slot therein which receives opposed shoulders extending from the cylindrical member through another diametrical slot. Axial translation of the collar releases or secures a tool in the bore while the chuck is rotating at operating speed.