Abstract: A cutting or drilling spindle and a tool unit supportable within the spindle for rotation with the spindle wherein the tool unit is provided with radially extending protrusions which can be received within corresponding inner radially spaced recesses within the spindle. The radial protrusions of the tool unit comprise balls support adjacent the exterior surface of the axial neck of the tool unit by a cage and which operate in such a way that during axial insertion of the tool unit into the spindle and locking, the radially outwardly extending portions of the balls will be engaged in the spindle's recesses. The balls are relatively movable such that if they are not properly aligned with the recesses when the tool unit is inserted into the spindle, the balls facilitate correction so that the protrusions of the tool unit will match the indentations of the spindle.

Abstract: A tool holder for easy and quick insertion in and removable from a high speed spindle of a machine tool. The tool holder is positively driven by the spindle by means of a quickly engagable and disengagable clutch. A drive adapter is insertable in the bore of a conventional spindle and has a drive clutch element which is disengagably connected with a complementary drive clutch element of the tool holder. The tool holder also has a resilient, flexible means in the form of an O-ring which frictionally engages the interior of the spindle so as to prevent inadvertent removal of the tool holder when reverse rotational forces are applied on the tool or at lower speeds of the spindle. The resilient, flexible means is centrifically urged in tight frictional engagement with the spindle when the latter is operating.