Keyless High Torque Drill Chuck 0.512" Cap., R8 Mount Size, SteelMfr #: R 8 High precision keyless drill chuck arbor is integrated into the internal socket of the drill chuck. This integrated design makes it impossible for the arbor and the drill chuck to become accidently separated, providing a unit of greater rigidity and precision. As a result of its compact design, accumulated run out is reduced to a minimum. Self tightening feature automatically increases gripping force proportional to increased torque to