Projecting ornament of the character of those upon the edge of the central piece, fig. 744, may be turned upon the work in the solid, or its cylindrical edge may be recessed to receive inlaying, when held between centers in a useful variety of the upright chuck the description of which was reserved for this chapter. This may be made of a hollow wood plain chuck, or for larger work, such as an ornamented ring surrounding the upper part of a pianoforte leg, as a box, formed of flat pieces of wood firmly screwed together around a square base. The two pointed center screws, frequently also of wood, are placed opposite to each other in the diametrical line of the chuck, and support the work as a wheel, figs. 753. 755, by corresponding hollow centers made axially in its two surfaces.
The work is first prepared to shape, turned concentric, but left everywhere in excess of its finished form, more especially upon its two ends, which each receive a deep conical hollow center. The cylindrical or curved edge, is then marked with a circular line for the vertical position, and divided across into equi-distant parts, for the number of the ornaments; every intersection being deeply indented with a center punch. Placed in the chuck, the work held rather stiffly between the pointed center screws, is shifted laterally by slackening the one and tightening the other, and shifted round between them, until one of the center marks is adjusted to the mandrel axis. It is then fixed in this position and sufficiently securely for turning, by one or two long joiner's screws, passing through one side of the chuck and indenting the end face of the work. The ornaments may be turned as plain hemispheres, hollows, grooves or other forms, or these surrounded by mouldings, each member of every separate ornament concentric. One being turned, with the tools held and advanced as described in previous examples of turning upon the edge; the two binding screws are sufficiently withdrawn to permit the work to be moved round upon the center screws, so as to place the mark for the succeeding center in the axis of the lathe, and so on for the remainder. Every ornament may be completed seriatim, but, as the binding screws make a number of indentations in the end of the work corresponding to the number of ornaments turned upon its edge, every one may be readily returned to, to gradually produce the series, or to make alterations.
The work is marked with more than one circular line, divided accordingly with the division plate, when more than a single series have to be turned upon it, as for placing corresponding ornaments at both margins of the edge. The diagram, fig. 754, shows the edge marked with lines for three series of centers, which are arranged for the circles to cut into one another to produce incised eccentric ornaments, somewhat the character of figs. 740. 742. In such cases one series of circles being turned, the work is shifted laterally by the center screws, and another placed opposite the mandrel axis; the external and internal diameters of the forms of all the raised or incised work, being in every case turned to fit the profile of a thin template, to ensure their similarity. For the analogous ornamentation of conical edges, as that in fig. 745, the two center screws pass through apertures in the sides of the chuck, placed in the diametrical line, but pierced at the appropriate angle. The radial turning completed, the work is in all cases mounted between the lathe centers to finish the forms of the end surfaces, and to turn any portions of the edge that may require circular reduction.
Pig. 753. Fig. 754. Fig. 755.
Discs and rings turned from the wood mosaics, known as Tunbridge ware, form an effective variety, when inlaid in the edges of cydindrical work, in apertures turned in the manner just described; as also for surface ornamentation, inlaid after the modes mentioned pages 539 - 543. These mosaics may be obtained; but the long strips of wood, of triangular, square and rhombic sections composing them, may be very easily cut out with the circular saw and combined into suitable patterns, by following the simple expedients given at length, Chapter XXVII (Saws. Section I. - Division Of The Subject - Forms Of Saw Teeth). in the second volume. More effective results may be obtained if the mosaic be formed of a less number of larger pieces, as explained in relation to figs. 744 - 746 Vol. II.; this avoids the excess of minute detail, which generally aimed at in the manufactured specimens, is not always desirable for the particular purpose in view.