Abstract: A copying machine has a sliding table slidable on a board. A pattern plate and a work piece are clamped on the sliding table by a clamping device. A cantilever arm is pivotally coupled on the board. A motor is fixed to the body. A casing is pivotally coupled to the arm by a pin. A shaft is rotatably supported on the casing and is driven by the motor via a belt. A roller and a tool are fixed to the shaft. When the tool contacts the work piece, the casing is caused to rotate away from the arm. The roller is caused to move gradually toward the pattern plate by a resilient force of the belt so that the tool can gradually machine the work piece and so that the tool will not be easily damaged.