An attachment (10) for use with a power tool (12) which can conveniently convert a rotatable chuck (14) or adapter (78) used with a first bit device (22) to usage with a second bit device (36) and vice versa. Either first or second bit device can be used for drilling, fastener driving or for other operations, however the preferred configuration is use with a first bit device for drilling pilot holes and a second bit device for driving of a fastener into the freshly drilled pilot hole. The attachment (10) is easily detachably securable with respect to any chuck (14) or adapter (78) which has a rotating cylindrical surface (18) with a locking aperture (20) therein. A capping ring (52) may be positioned in an annular slot (42) to retain a resilient member (48) positionable within an annular groove (40) for facilitating biasing of a locking pin (44) into a locking aperture (20) on the rotatably driven cylindrical mounting surface (18).