The machine shown in Figs. 1, 2, and 3 has been devised by Messrs. Junker & Ruh, of Carlsruhe, for cutting internally-toothed gear-wheels. The progress of the work is such that the wheel is pushed toward the tool by a piece, n, provided with a curve guide, and that the tool is raised and separated from the wheel after a tooth has been cut, in order to allow the wheel to revolve one division further. The tool is placed in a support, b, which is fixed to the upright, d, in such away that it may revolve; and this support is connected to the frame, a, of the machine. A strong flat spring, f, constantly presses the tool-carrier, b, toward the upright, d, as much as the screw, g, will permit; and this pressure and the tension of the belt draw the tool downward. The screws, g, determine the depth of the cut, and compensate for the differences in the diameter of the tool. [Illustration: MACHINE FOR CUTTING ANNULAR WHEELS.] The wheels to be cut are set by pressure into a wrought iron ring, with which they are placed in a sleeve or support, h. The connection between the two is assured by means of a nut, c. The axle of the support, h, is held in the upright of the carriage, k, which receives from a piece, l, placed on the driving-shaft, n, a slow forward motion toward the tool, and a rapid motion backward. The trajectory curve or groove of special form of the piece, l, in which moves the conducting roller, o, of the carriage, is not closed everywhere on the two sides, in that the guides that limit it extend only on the part strictly necessary. This arrangement permits of the roller being made to leave the trajectory in order that the carriage may be drawn back to a sufficient distance from the tool when the wheel is finished, so as to replace the latter by another.