A complex apparatus for the precision tracing of geometric lines or exact graduated scales on observation and measurement instruments. The dividing engine basically consists of a rotating platform on which the circle or the sector to be engraved is mounted, and a mechanical system that rotates the platform at the desired angle. This is achieved by cutting evenly spaced teeth on the edge of the platform and meshing them with an endless screw of appropriate size. The rotation of the platform is equal to the rotation angle of the screw divided by the number of teeth on the wheel. If the mechanism has been constructed accurately, the platform can therefore be rotated at very small angles. The circle to be divided was placed on the rotating platform, taking care to center it on the platform's rotation axis. The operator then turned the screw at the angles corresponding to the angular distance required to separate two close divisions on the scale to be engraved. After each movement, a burin engraved a line on the edge of the disk to be divided. Dividing an arc or circle was a particularly delicate and demanding task.