The specimens described under this head consist either of main central figures, into which other portions are inserted eccentrically, or they have the main figure divided in several pieces, built up and connected by the other parts; in some few cases attached portions are cut out and shaped by other means than turning.

Those least removed from the works in the previous chapter, such as the Watch stand, fig. 687, about five inches high, in which the circular base and the tray above are connected by four or five short columns, have the additions parallel with their axes. All portions of this and of most of the succeeding examples, may be turned in softwood, hardwood, or ivory. The columns made from single pieces are nearly parallel, having mouldings at either end for the capital and base, beyond which both ends are prolonged as cylindrical pins for attachment. One column being first completed as a pattern, the remainder are formed of precisely similar dimensions, attained in each seriatim by first turning down the terminal pins to the same diameter, with the length of the remaining cylinder between accurately maintained; and then from that by measurements, turning the shaft, base, and capital to exactly accord with the pattern. The base and tray turned to form, they have circular lines struck upon the upper surface of the one and on the flat under surface of the other, to determine the position of the holes to receive the pins; the two circles being of precisely the same diameter that the columns may be vertical. That upon the base as the smaller piece is marked first, and sufficiently within the margin to prevent the foot of the column extending beyond it; the diameter of this circle is then exactly copied in striking the corresponding line upon the upper and larger piece. A lead pencil supported on the rest may be employed, when, should the dimensions of the second circle not precisely agree with those of the first, others may be marked within or without it, or the pencil may be slightly shifted so as to thicken the line until they do. The pencil would suffice for fig. 687, and its marks are easily removed with glass paper; for greater precision, the compasses opened to the diameter of the circle may be employed as described upon the softwood surface; and for nearly finished work, the pencil used to mark the circle under measurement is supplemented by a fine line carefully cut with a point tool; but both the latter require the surface to be subsequently turned smooth to remove the lines, after the holes have been bored or their centers sufficiently marked. The two circles are divided into the requisite number of parts with the division plate, and marked across with the pencil or scratched with a line, page 126; and the work removed from the lathe, has the several centers carefully indented with a center punch.

In softwood, the holes to receive the pins may be made with an ordinary center bit; the correctness of their positions being ensured if a fine hole be first bored with a wire drill or a small spoon bit in each center punch mark, for the guidance of the point of the center bit, all the bits being mounted in chucks and running truly in the lathe; and the work held upon a parallel piece of board, being advanced by the flange of the popit head. The holes may also be bored in hardwood with drills running on the mandrel, but it is better for this material and almost a necessity for ivory, to mount the work upon a wooden surface chuck, page 240, that the centers marked may be successively placed in the axis of the mandrel and turned out to size with the hand tools. In all cases it is advisable to make the holes first, and then to slightly reduce the pins to fit them.

The amphora supporting the watch, in fig. 687, is in two pieces divided immediately below the head, which should be too large to pass through the bow; the neck is hollowed to receive a pin turned in the solid with the head, which is withdrawn and replaced after the bow has been placed around the neck. The vase upon fig. 686, is of similar construction.

Practical Examples Of Combined Plain Turning Execu 400368

This watch stand, as also fig. 682, has a square plinth, turned in the manner described in the succeeding chapter, and partially bored with a central hole to receive the pin for its attachment, which pin or external fitting is turned in the solid beneath the foot of the large vase.

Inclined columns, of which the Watch stand, fig. 684, about seven inches high, affords a small and fig. 747, a larger example, and all pieces so placed, may be variously attached to the surfaces they connect. Upon flat surfaces, as in the sections figs. 688. 690, the shafts are separate pieces, reduced at the ends. In the first figure the pins on the shafts are turned in the ordinary manner, having square shoulders and pass through the shaded piece, which may represent either the capital or the base, into the surfaces above or below. The separate capital or base finished to form but left solid, is then mounted centrally in the gap of fig. 318 or 319, held, the first, by its extreme upper and the last, by its under edge, the surface projecting beyond the front of the chuck, but parallel with it. One side lying in the direction of the opening of the chuck is then gently depressed, the work therefore rotating upon its diametrical line, until the face arrives at the required angle, as measured from the surface of the chuck; the screw or ring is then tightened, and the exposed face of the work reduced with a flat tool upon the arm rest, until it is again parallel with the surface of the chuck, and of sufficient diameter for the shaft. Similar angles upon all the pieces turned, may be ensured by first adjusting the work to a template, fig. 689, having two long projections bent at right angles to lie on the surface of the chuck; equality in thickness being gradually arrived at, by frequent measurement of the edges of the different pieces through the gap of the chuck, as the face of the work is reduced. The work still in the same position then has a center made in it with a point tool and is pierced with a small drill, this hole being afterwards enlarged to the diameter of the pin on the shaft; all the turning on the surface and in the aperture, being carefully and gently conducted to avoid displacing the work. Work requiring more accuracy may be mounted axially, upon the sloping face of a wood chuck, fig. 321, this however is rather tedious for numbers, each piece having to be glued down.