CHAPTER VI.
WORKING OUT THE BACK.
Passing on, I draw your attention to the working out of the back.
I show you, fig. 10, what must be drawn on the back and belly (on the flat, of course) before a chisel touches the wood for excavation. The blocks at either end speak for themselves, they having been fashioned to shape out of Swiss pine, and planed and squared so as to be glued square where you see them marked, later on. And be sure they stand one-and-a-half inches high in the rough, for a reason I will give you later, and about five-eighths of an inch thick, to about the breadth you see on fig. 10.
| PLATE X. |
Before, however, you can do anything in hollowing out the back, you will have to provide yourselves with a bed in which your table must firmly rest while you do so. Therefore, purchase a block of dry beech or birch, about one-and-a-half inches thick, sixteen inches long by eleven inches wide, and lay your finished back in the centre of it, tracing the whole outline, button as well, distinctly thereon; and having done so, cut by the outline inside all round to the depth of about one quarter of an inch, and from this basis proceed to make, as nearly as possible, a counterpart of the model of your back, but reversed, of course. And get all the tool ridges well levelled with rough to fine sandpaper; and, when you lay in your table for cutting, place a strong piece of brown paper for it to rest upon, not only to prevent it in any way scratching the fine surface of your wood obtained at so much trouble, but it enables you to shake off it quickly any residue of coarse dust or small cuttings that will creep under the wood upon which you are working; and so you get on rapidly and cleanly.
You will notice that I have again drawn the guitar line, and at a distance from the outline, so that a sufficiently flat surface is allowed for the ribs to rest firmly upon later. And I cut all round this line just as an indication, merely as a starting point from which to work more deeply all over, until I arrive at a point when the calipers, [No. 34], test the thicknesses roughly—which is by the way. For I have first to cut three cross channels, at the upper, middle, and lower nodal points, fig. 11, at such a depth that I caliper good three-sixteenths of an inch at the centre of middle groove, one-eighth of an inch upper and lower, falling away very little to all edges for the present. And I draw a distinct pencil mark through each groove, so that I must be a poor workman indeed if I go through the wood through these bars, as I have known some novices to do, or cannot gauge pretty well all over by their aid before using the calipers.
| PLATE XI. |
But you who, when beginning to cut out back or belly, having no sort of experience whatever, must use every care possible, and keep calipers [No. 3] (double) going constantly, as, with their aid, you will at once see by the outside half the thickness registered at the inner; then you can pare away with gouges, small and large, and with spoke shaves, [Nos. 48 and 53], until you get a fairly sloping and somewhat level surface from bare three-sixteenths of an inch in centre to full three-thirty-seconds of an inch all round by the edges, as shown by calipers.
And thus I come to the first rough thicknesses of the back; and I damp the surface all over as I did the outside, and dry it carefully; for you will understand the necessity for this carefulness, there being some fear of slight warping from the true flatness now the wood is thin all over, if quick, artificial heat be adopted to draw the moisture.