A high-speed, hand-held attachment for flex rotor shafts of power rotary tools, and also for direct attachment to power rotary tools without flex rotor shafts, that converts rotary motion to reciprocating motion for precision control of cutting, carving, sawing, chiseling, filing, sanding, and engraving on delicate work pieces. The attachment is one assembly comprising a one-piece front one-piece enclosure (20), a rear one-piece enclosure (30), a high-speed bearing (22), a one-piece rotating piece (40) with integral cam groove, a one-piece reciprocating piece (50) with an integral cam follower on one end and with its other, exposed end accomodating the attachment of a chuck or collet and with geometry to prevent rotation, and a thumbscrew (32). Rotating piece (40) attaches directly to the rotary power source and provides the cam action drive to reciprocating piece (50). Bearing (22) provides rotative support for the other end of rotating piece (40). Reciprocating piece (50) slidably mounts in front one-piece enclosure (20). Front one-piece enclosure (20) and rear one-piece enclosure (30) are attached to each other and maintain proper alignment for rotating piece (40), bearing (22), and reciprocating piece (50). Thumbscrew (32) secures the attachment to the flex rotor shaft of a power rotary tool. A tool holder / collet is attached to the exposed end of reciprocating piece (50) whereby numerous types of cutting tools may be utilized. Alternative versions of the rear one-piece enclosure, (30A) and (30B), described herein, allow for attachment directly to power rotary tools without flex rotor shafts. Alternative versions of the reciprocating piece, (50A), (50B), and (50C), and of the rotating piece, (40A), are also described herein.