Scale, two-thirds of an inch to a foot.
Fig. 11.
Remark.—M. Hamel advises that in making the sound-board the table should be left 3 inches longer at each end than the actual box beneath, expressly to afford a bearing for the ends of the sliders during this business of planing them. If this suggestion is not followed, the projecting ends of the sliders will require separate attention.
The three upper boards may now be brought down upon the finished sliders and bearers, and a couple of iron pins or dowels may be let into each of them and into the bearers and table beneath, near their extremities, for the purpose of confining them temporarily in the exact places which they are to occupy. Dress over now the upper sides of the three boards, which do not, however, require attention to absolute truth.
8. We cannot yet bore the holes for the pipes. Before we can do so we must prepare yet another board or boards of clean pine, ⅝ or ¾ inch thick, 4 feet 6 inches long, and 15 inches wide, for the rack boards through which the pipe-feet are to pass, and which are to maintain the pipes in an upright position. If you have two upper boards the division should occur between those of the 8-feet and 4-feet stops. Pin down your rack-board upon the upper boards with brads here and there near the edges.
Let us now consider for a moment. We have made our box of fifty-four transverse channels or grooves, and its top consists now of four layers of wood—namely, the table, the sliders, the upper boards, and the rack-boards. Through these four layers of wood, at the proper places, are to be bored holes of various sizes clear through into the channels; but it is plain that the holes in the rack-boards will always be much larger than those in the three other layers, because the rack-boards are to be ultimately raised about 5 inches above the upper board on legs or pins, and will therefore receive the thick part of the conical pipe-feet, while the holes in the upper board will only receive their tip or small extremity. But the centres of the large holes in the rack-board must coincide accurately with the centres of the small holes beneath, and we shall therefore proceed to mark the exact spots where each of the holes will commence.
By the aid of your marked rule, trace a line on the front and back cheeks of the sound-board, showing the centre of each groove. From these points draw lines across the rack-boards. It is evident that all holes bored through the four layers of wood at any point in any of these lines must terminate in a channel. Draw lines at right angles to the last, showing the widths of the sliders and bearers; it will then be further evident that we cannot easily get wrong in boring the holes so that they may penetrate the sliders at the exact points intended. But the actual boring, with certain consequences or contingencies belonging thereto, must be reserved for the next chapter.