The more ornate example, fig. 733, drawn from a finished work twenty two inches in total height, shows the back, of which the upper portion is shaped out as part of the design. The external frame turned in cubes and beads from pieces of square section - for which, see the concluding chapter, - has the vertical lengths terminating in pins, inserted in the slightly larger terminal cubes of the similar horizontal piece, and in the circular pendants below. The latter join the ends of the plain horizontal bar, the center of which, left square, is attached by screws to the flattened side of the base of the lower tazza, which base also carries the central pendant; these parts are all flattened only so far as necessary for their attachment to each other or to the back, except the bowl of the tazza, which is divided parallel to its diameter to rest in contact with the surface of the glass. The upper tazza and its pendant are left circular, except the largest diameter of the latter, which is flattened, and fixed by screws to the square center of the horizontal portion of the external frame. The ornament above is of three pieces; the columns have pins at their lower ends passing into the side pendants, above they are flat, and meet the end surfaces of the half of the large ring forming the arch. The arch and some of the larger portions are turned in mahogany, dyed black and polished to agree with the remainder of the work, which is of African black wood or ebony.

The central enrichments of the spandrels, flat discs ornamented by sunk eccentric steps and mouldings, and attached by a central pin in holes in the surface of the foundation plate of the frame, are the only portions requiring description. To about three inches diameter, such pieces may be turned upon a wooden cement chuck, having a short and fine central wire, as described page 239. The discs are first turned to the required diameter and thickness, flat on both surfaces and their external margins to a moulding; the centers for the trefoils, figs. 734. 736, are then marked on the under surface, and a fine hole made in each center for the wire of the cement chuck. Attached upon the chuck with the central wire in one of these eccentric holes, the first of the three circular forms composing the ornament, indicated by fig. 736, is turned in the face, sunk as a series of steps and mouldings each below the other, the center being turned as a flattened hemisphere standing upon the deepest flat surface. This completed and polished, the disc is released and replaced upon the chuck, with the wire in a fresh center to turn the second. The first then serves as a gage for depth, as the tools cut across its steps and mouldings in repeating them in the second; while the central hemisphere of the first being below their level, remains untouched by the tool in turning the larger diameters of the second. The third leaf intersecting the two previously turned, completes the figure. In fig. 734, and in the quatrefoil, fig. 738, the lower circles cut across the center, in these therefore and in that employed in the mirror, the central ornament is inserted, its pin passing through the disc into the form to which it is to be attached. The leaves of the cinquefoil fig. 737, have central concaves, while the circles of their margins leave portions of the first step ; the central portion thus left, may if desired, be subsequently turned down to the general level with the work mounted centrally.

Fig. 734. Fig. 735. Fig. 736.

Plain Turning Applied To Surface Ornamentation Par 400389

Fig. 737. Fig. 738.

Work of increased size is turned more safely, when carried in a cavity sunk in the face of a wooden surface chuck, fig. 735, a method more facile and exact. The wood surface chuck is first turned true, mounted centrally on a screw worm chuck having a large flange, and coincident diametrical lines are marked across its back and front; a hole is then bored on one line, so far from the center of the chuck, as the distance between the center of the disc and the centers of the series of eccentric circles to be turned in it. The surface chuck mounted by this hole upon the screw worm chuck, then has a flat eccentric cavity, the depth and diameter of the work, turned in its face; after which it is replaced for use with the screw in the original central hole. The work, divided with lines upon its margin into the number of leaves required, is placed in the cavity, with one of these lines agreeing with the diametrical line on the front of the chuck, retained in position by either one or two screws, usually joiner's wood screws, which pass through the edge of the chuck and that of the cavity, to slightly bear upon the edge of the work. One complete form being turned in the work in the manner previously described, the others follow, the screw being released and the work refixed, with every mark in turn against the line on the chuck; or which is sometimes more convenient, the forms may be gradually produced, the upper mouldings being completed at every center before proceeding to turn the lower. The cinquefoil represented on the chuck, has had the disc subsequently mounted centrally, held by its edge, and the center cut through, leaving it a ring. The ordinary flat and other hardwood tools are employed, held horizontally and advanced gently, so far as possible always cutting straight forward from the face, the rest placed across the surface of the work. A narrow flat tool keenly sharpened upon both sides and the end, is used to remove the bulk of the material, widening and deepening the grooves a little at a time; this tool shapes all steps and surfaces, leaving the edges and faces sharp and cleanly cut, it is followed by tools of other forms for those parts to which it will not apply.