Rose Engine
A form of lathe in which the rotary movement of the mandrel may be combined with a lateral, reciprocating movement of the tool rest, the result being a movement of eccentric character. In this way many curves of an epicycloid or hypocycloid character and of great variety and beauty may be obtained by varying the rate of speed between the lathe mandrel and the lead screw, or splined rod which governs the motion of the tool post in the slide rest. The change gears are handled as in the ordinary engine lathe. Another form of this engine has a very heavy head, formed of a series of disks, circular in form, and placed concentrically on the shaft, so that they resemble a cone pulley having a large number of steps. These disks, instead of being true circles, are formed of a great number of facets, so that the discs constitute polygons of 64, 120, 180, etc., sides. The central mandrel bears an eccentric chuck and has lateral play, so that the facets, striking on a rigid roller, throw the mandrel alternately in and out of center, thus bringing the work regularly to and away from the cutting tool, making the tool cut a lozenge-shaped chip each time a facet on the disc is encountered by the roller. The work being held eccentrically in the chuck, these chips, or digs, are very fine and close at the center, and enlarged proportionately as they reach the outside of the watch case or other object being ornamented. The work is done with tools which have been sharpened and polished so carefully as to make a "bright cut" on the metal, and the operator turns the lathe with one hand and watches the progress of the work with a glass.