A "snap-in" bit chuck assembly for a rotary hand or powered tool, includes an elongated body having a hex shank at its rearward end, an elongated retraction collar slidably disposed on the body, and an outer retaining collar fixed to the forward end of the body. The body has a coaxial hex socket formed therein to allow a reversible tool to be inserted thereinto. A slot is formed in the body, between the outer surface of the body and the internal hex socket. A coil spring surrounds the body, inside the retraction collar, and normally biases the retraction collar forwardly and biases a retaining clip toward the bottom of the angular slot. The retaining clip slides outwardly in the angular slot, against the bias of the coil spring, as the reversible tool is inserted, where a recess on the reversible tool is engaged and retained by the clip. The tool is removed by sliding the retraction collar rearwardly, to compress the coil spring and allow the retaining clip to retract back up the slot. The clip is directly engaged by the coil spring and has two legs extending about the body so that the clip is self-retaining. The clip legs extend around the body such that the retraction force on the coil spring is directed through the center of the coil spring to keep it coaxially aligned with the body.