The Young Mechanic / Containing directions for the use of all kinds of tools, and for the construction of steam engines and mechanical models, including the art of turning in wood and metal

by James Lukin

Fig. 21.

Fig. 21 represents a bar of wood—the side of the towel-horse, for instance—with a mortice cut through it at A, and others marked out at ab, cd. Below, at B, is a gauge, of which the construction and use will be explained presently. F shows how the feet are to be attached and cut. They are morticed while in a “squared-up” condition, and shaped afterwards according to fancy; sometimes they are left square, and knobs screwed below to make two feet.

These mortices may, of course, be of any desired length or width. Those required for the towel-rail sides will be 1¼ inch long by half an inch wide nearly. The planing of the strips may have reduced them more or less below the exact size specified, try therefore with the compasses what the precise thickness is of the ends, and measure that thickness on your two-foot rule. You now want to draw the lines a t, which I have represented as extending the whole length of the strip, and as all the mortices are to be alike, you may so mark them. The gauge B is of two parts, a sliding piece, C, and a rectangular bar of wood about 9 inches long and half an inch square. This slides stiffly through the mortice in C, and is fixed at any part by the small wedge D. This gauge you can easily make. It is not a mortice gauge properly so called, because the latter has two marking points instead of the one seen at h, and which may be the point of a brad driven in and filed up to an edge. Loosen the wedge slightly, and draw back the rectangular bar, or push it forward, until you think that the space between the sliding piece and the point is about that which is required on each side of the mortices, so that if you set the wedge firm, and resting the sliding piece against the edge of the board, cause the point to make a mark, and repeat this on the other side of the same face of the wood, there will be left between the marks thus made the exact width of the required mortice. Try it, and if not, give a tap to the instrument, and adjust it until the space is exactly correct. Then fix all firm, and holding it so that the little point will mark the wood, while the head or sliding piece is against the side of the board, run the tool from end to end, or run it along just where the mortices are required, using both hands. You will thus make the two long lines between which the mortices have to be cut. Now turn the wood over, and do the same on the other side. You are now quite sure that these lines, on opposite sides of the piece, agree exactly in position, which is the object of using a gauge; and as you have planed up a second strip to exactly the size of this first, you have but to repeat the process (no measuring being necessary) upon that; and you may be satisfied that thus far the two sides of the towel-rail will tally. You now set off with the compasses upon one of these lines the lengths of the mortices in their proper places, and at the points thus marked, using your square for the purpose, mark the end lines of these mortices; but when so doing, carry the lines across, as a b, c d, and down the sides and across the opposite side. With the square this will be easily done, the blade of it being laid flat, so that its edge becomes the ruler, while the handle becomes the guide or gauge resting against the side of the wood. At E, Fig. 21, this position of the square is shown.

By thus carrying round all the lines, you will have the mortices marked on both sides in exactly the same relative position, so that you can (and must) cut them half from one side and half from the other, using the chisel nearest to the size required, but always of less width (or length) than the mortice, because you must never cut out the guide lines, but must keep within them, only carefully paring the wood at last close to them. You will never cut mortices correctly, unless you thus mark the position on both sides, and work as directed.

The ends of the cross rails will not have to be cut into tenons, as they will fit as they are, only requiring to be glued into their places, when, if you have worked carefully, the whole will look well, and will be square and true, without twist; but if you did not plane up the sides square, you will find the towel-rail awry and unworkmanlike. Although, however, there is no necessity to make regular tenons in the present case, the usual way is to do so, and to fix with wedges, as in Fig. 15. After a mortice has been cut straight through a piece as directed, this mortice is slightly eased, or sloped off, as seen at a b, which is a section of one. The rail or tenon c is put through after being brushed with glue; and when in exact position, two wedges are glued and driven in at each end, as seen in the drawing. After all is dry, these wedges being firmly united to the rail, as seen at k, prevent it from being drawn back or moved. Nearly all mortice and tenon joints are fixed in this way.

As I am describing this kind of work, I may as well explain the method of marking and cutting tenons, as it will answer not only for affixing the feet, as shown in Fig. 21, but for all similar work.

Fig. 22.

In Fig. 22, I have illustrated the mode of marking out tenons, and at D is a double tenon, which is in wide pieces often substituted for the single, and makes an excellent joint. The longitudinal lines e, f, g, h, are marked as before with the gauge, whether for single or double tenons; the line a b, with the assistance of the square; the cheeks, c and d, are then cut off entirely with a fine saw, called on this account a tenon-saw,—and care must be taken as before not to cut out the guide lines. If, instead of the outer cheeks, the piece between them is to be removed to make a double tenon, this must be done with mallet and chisel, after carefully sawing down the lines x y; and the chisel is to be used first on one side and then on the other, by which means the shoulder will be cut true to the guide lines. If, however, the cut across should curve a little downwards like n, it will not much matter, so long as the edges fit closely. It is nevertheless better to cut straight across. The outer cheeks of this will be marked and cut as in the single mortice (Fig. 22).