A downhole tool assembly for use in directional drilling operations. The assembly has a housing, a chuck, a cutting tool, a hub, and an elongate drive member. The housing has a spindle for supporting the hub and chuck for rotation thereon. The chuck is connected to the hub and has a non-circular interior surface and a box for supporting a cutting tool for rotation with the chuck. The elongate drive member is disposed within the housing, the hub, and the chuck. The drive member is operatively connected to the inner member of a dual-member drill string for rotation independently of the housing. The drive member has a non-circular external surface corresponding to the non-circular interior surface of the chuck. The pin end of the drive is slidably receivable in connector free torque-transmitting engagement with the interior surface of the chuck to drive rotation of the cutting tool, chuck, and hub independently of the housing.