Rose–en′gine lathe.
（Engraving.) A lathe in which the rotatory motion of the lathe and the radial motion of the tool combine to produce a variety of curved lines. The mechanism consists of plates or cams set on the axis of the lathe, or suitably rotated and formed with wavy edges or grooves which govern the motion of the cutting point toward or from the center. [1984] In another form, the combined radial and rotary motion is inherent in the work, the tool being stationary. In this case, the center of the circle in which the work revolves is not a fixed point, but is made to oscillate with a slight motion while the work revolves upon it. The mandrel upon whose end the work is chucked does not rotate in stationary standards like those of a common lathe, but the standards form part of a frame which oscillates upon a horizontal axis below the bed and parallel to the mandrel axis. The work is fixed in a chuck at the extremity of the mandrel, and the tool is held by a slide-rest, and adjusts it to the radius of the rose or figure intended to be cut. The oscillating motion is given to the mandrel by means of metallic rosettes or wheels fixed upon the mandrel, each having its edge or periphery indented and curved with a waving line. The rosettes are acted upon by a small roller at the end of a bar supported from the bed. As the mandrel revolves, the wavy periphery of the rosette is applied to the roller, which moves on a stationary axis and causes a vibratory motion of the mandrel as its frame moves to and fro on its axis. The mandrel contains a number of rosettes of different patterns, and the governing roller is slipped on its axis so as to act in conjunction with any one of the rosettes, according to the pattern required. Rose-engines and geometric lathes vary somewhat in their details, but agree in the general features that the work is performed by a combined rotary and radial motion. If the center of the rosette and the axis of rotation coincide, and the tool receive an oscillation radial as to the said center, a wavy circle is produced. If the chuck and its mandrel, while rotating, are oscillated back and forth on a parallel axis (as previously stated) while the tool is stationary, the same effect — a wavy circle — is produced; the change merely being to move one part or the other, relatively to its fellow, in the degree and proportion. If the center of the pattern do not coincide with the axis of the mandrel, the effect will be an eccentric figure. If the radial oscillation be given to tool or chuck, in addition to the former conditions, a wavy eccentric figure will be produced. (See chuck; eccentric.) If an oval or elliptical pattern be required, it may be obtained by means of an eccentric guide or ring of brass fastened to the puppet of the lathe close to the collar in which the neck of the mandrel runs. (See chuck; oval.) If the governing eccentric be wavy, the effect will be a wavy ellipse. By governing squares or other geometric figures, patterns of the required conformation are obtained. By a suitable disposition of the parts involved in the circular and radial motions, the tool is caused to make the peculiar line required within the limits of the said figure. By means of a straight-line chuck, the patterns of a rose-engine are made to follow in a straight instead of a circular direction. Notable instances of the uses of this class of instruments are to be found in the machines of engine-turning watches, and those for making the complicated figures termed lathe-work, which abound on the obverse and reverse faces of greenbacks and other bank-notes.
