Читать книгу The Young Mechanic - James Lukin - Страница 9

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The exercise of a boy’s mechanical tastes upon works of practical utility is, of course, far preferable to its expenditure upon mere trifles, made one day to be cast aside and destroyed the next; and as there is scarcely any household that does not need its furniture repaired or added to from time to time, I shall now give directions for the construction of one or two articles that seem to be within fair scope of a young mechanic’s abilities. The first is a plain, useful table, without a drawer, and with square legs, because without a lathe the latter cannot be made ornamental; and lathe work will occupy some future pages, since it is necessary first to give the young mechanic a fair insight into the principles and practice of plain carpentry and joinery.

The very young mechanic, so far as my experience of him goes (and it is rather extensive), makes his early attempt by sticking the points of four nails into the corners of any tolerably square piece of board he can lay hands on. His next attempt, when he has risen to the dignity of a knife and gimlet, is to place four wooden legs at the corners of a similar board, which, if the said legs are glued in (by which a wonderful mess is always made of the structure), is considered a great feat, and worthy of the admiring patronage of fond parents and playmates. Now, a table does not consist of any such arrangement of pieces, although I certainly have seen sometimes, in the cottages of the poor, a three-legged affair of this nature, which is just nothing more than a magnified milking-stool. We cannot content ourselves now with anything of the kind. We shall have to work away with plane and chisel and square, and with neat tenon and mortice joints first construct the frame upon which the top will be placed, and then finish it secundum artem, the English of which, as I am writing to boys, I shall not reveal.

The table shall be 3 feet long, 1 foot 8 inches wide, 2 feet 4 inches high; the top board being half an inch thick when planed and fitted, for which it will therefore be required to be three-quarters of an inch in the rough. The legs demand attention first. Plane up strips cut from a 2-inch board, and let them be exactly 2 inches wide. These must be worked up with the greatest possible accuracy, or it will be impossible to fit the framework so as to make the table stand truly or bear inspection. After four such strips have been planed up, cut a piece from a half-inch board, or from a board that will plane to half an inch. Let this be 4 inches wide and 9 feet long, and be sure to plane this also truly, and to make the edges square to the sides.

Fig. 23.

If you have no strip that will answer of 9 feet long, you can cut two or more instead, remembering that you will require two pieces each 18 inches long and two of 2 feet 9 at the least, all as nearly alike in width as possible. You have now all that you will need for the framework of your table—the top may be left till the rest is fitted. Now you may proceed to cut the requisite mortices in the legs, which you will understand by sketch Fig. 23, which represents one corner of the table before the top is added. There is no more difficulty in this than in the previous work, except perhaps that somewhat more care is requisite in squaring up the several pieces and cutting the mortices with accuracy. Use the gauge as before in marking the mortices, trying it until it is so fixed that it will leave the proper width of the holes, namely, half an inch (which is the thickness of the strips which are to form the framework). This is upon the supposition that your gauge has but one marking point: but to explain its use.

Fig. 24.

I shall now introduce to your notice a regular mortice-gauge of two points, which is vastly more convenient. This is represented in Fig. 24. The main stem is grooved along its length on one side with a dovetailed slit, that is, a groove which is wider below than above. This is generally made in a brass plate attached to the stem of the gauge, but sometimes in the wood itself. In this slides a slip of brass which can be drawn back by pulling the knob A, or by turning a thumbscrew at one end, as in the more expensive gauges. One of the marking points is fixed in the end of this slide, the other in the wood (or metal) beyond it, at B, and when these are allowed to be together they form but one point, being flattened on one side, so that they will fit accurately against each other. Thus it is easy to separate the two points at pleasure to the exact width of the required mortice. By means of the wedged sliding piece C, we now have merely to determine how far the edge of the mortice is to be from one side of the piece. Thus, suppose that in the present case we should prefer to have the side of the frame nearer to the outside edge of the legs than to the inside, we can so arrange it easily; but we must then take care to gauge all alike, either from the inside edge or the outside. We do not, therefore, with this kind of gauge work from both edges, and leave the space between the lines for the width of the mortice, but we work from one edge only of the piece of wood, and mark the mortice at once in any desired position. I need hardly repeat, that for any particular job, a very good substitute for such gauge can be made by driving two small nails into a strip of wood cut with a projecting piece to serve instead of the movable head.

Fig. 25.

Let us now proceed with the work in hand. One of the legs of the table, before being worked into shape, is shown in Fig. 25; the dotted lines show how it will be eventually sloped off below the mortices which carry the top frame. These mortices must not now go through the legs, and therefore you will have to be very careful to hold the chisel upright, so as to insure the squareness of the frame when put together. The mortices being in adjacent sides, will of course meet, but it will be advantageous to cut those which are intended to receive the two longest strips, viz., the front and back, rather deeper than the other two. First set off an inch from the top of the leg at the line A B. If less than this intervenes between the top of the mortice and the end of the leg, you will probably break the piece out and spoil your work. As the side boards are 4 inches wide, and must come flush with the top of the legs, you will have to cut them like C, and there will be 3 inches left for the tenon, all of which may be left, as the wider this is the more hold it will have on the legs into which it is to be glued. It is plain, therefore, that the mortice will be 3 inches long and half an inch wide; and when you have marked it to this size, take care to cut it accurately, because if it is too small, you will break out the piece between the mortices when you try to force in the frame pieces, and if too large, you will scarcely get the whole to remain secure. Work therefore exactly to gauge. It is usual to keep these side and end pieces more to the outside of the legs than the inside, as F, where you are supposed to be looking at the inside corner; and if you look at D (which shows the top or cross section of a leg, as if after the pieces were fitted you had sawn off the leg close down to the mortices, exposing them to view), you will see that by thus keeping near the outside edges you get both mortices deeper than if you cut them, like E, in the middle of the sides of the leg. Of course, the deeper these tenons are let into the legs, the stronger their hold will be. There will now only remain to warm all the pieces and glue them into their respective places, with the precautions before stated as to the thinness of the glue and speed of the operation. See that all stands square and true; if not, a tap here and there as required will set it straight, and then let all stand till dry.

I have told you to cut the side and end pieces 18 inches and 2 feet 9 respectively, so that if the mortices are 1½ inches or so deep, your frame will be about 1 foot 6 inches wide, and 2 feet 6 inches long. The top, which is to overlap as usual, will be now prepared as follows. It will not be possible to make this of a single width of board; and nothing will more fully test the young workman’s skill, than planing the edges of two pieces so that they shall fit accurately together. It must, nevertheless, be attempted.

Cut two pieces of three-quarter-inch board, and plane the sides as accurately as possible. Then set them up edgewise, either singly or together, and plane the edges with steady, long strokes of the longest plane you have, set fine—that is, with the cutting edge projecting but slightly. Try each singly with the square from end to end, and then lay them on any perfectly flat surface, as on your bench, or on a table, and see whether the edges lie close all along. Remember, too, that they may do so when one surface is upwards, and not when turned over, as will occur when the edges are not square to the sides. In cutting out the pieces, therefore,—which, when finished, are to be together 1 foot 8 inches,—you should make them 1 foot 9, so as to allow you a whole inch to waste in planing and fitting. When both are as true as you can get them, lay them down near together, and brush the edges with boiling hot glue. Then immediately put them together, and rub them a few seconds one against the other, till they seem to stick slightly. Then leave them in their exact position, and drive a couple of nails into the bench against the outside edges, so as to keep them together, or in any other way wedge them tightly in position until they are quite dry. When the glue is hard which has been squeezed out along the joint, you may run a plane all over the united boards, and you ought hardly to see the joint, which will be nearly as strong as any other part.

This top has now to be attached to the frame, as follows. Cut some pieces like K in Fig. 25, and glue them here and there along the inside edges of the frame, so that one side of them shall come quite flush with the upper edge. To these the top has to be glued. Lay it, therefore, with its under side upwards, upon the floor (I suppose the short pieces glued and dry on the frame), and having also glued the sides of the short pieces which will touch the under side of the table top, turn the whole upside down, with its legs in the air, adjusting it quickly. Its own weight will keep it in position until dry; or, if not, it is easy to lay an odd board or two across, and put some weights upon them. When dry, turn over your table, and plane round the edges where necessary; and, if it does not stand very well, trim the bottoms of the legs. Clean off glue, and rub any rough places with sandpaper or glasscloth, filling up any accidental holes with putty, after which it will be fit for receiving paint or stain, if it is not considered desirable to leave it white. The corners and edges of the top may be rounded off, to give a finished appearance.

I showed by dotted lines the usual shape of the squared legs. They are planed off, tapering from below the frame, and this should be done after the mortices are cut, and before fitting the parts together. The best way to insure equal taper of all the legs, is to prick off at the bottom of each equal widths from the corners or edges, and to run a pencil line from the point where the taper is to begin to these marks. Then plane exactly to the lines thus made.

Fig. 26.

Let us now consider what errors of construction are most likely to occur in working out these directions. First, it is possible that the framework may be out of square. This may proceed from two causes. In the first place, the side or end pieces may not be of equal length between the legs, owing to some one or two being driven further into their mortices than the others. To avoid this, which is not uncommon in many works of a similar nature, it is well always to mark the length that each is to be, irrespective of the part within the mortices, as Fig. 26, A and B. If the space on each between the dotted lines (carefully marked by means of a square) is equal, it is no matter whether C and D are also equal. We have only to take care to let them into the mortices to a greater or less depth, until the line comes exactly even with the inside edge of the legs. Again, it is possible that when the table is placed upon its legs, these may not rest truly on the floor. Probably one or two of the frame pieces run up like E, instead of standing at right angles to the legs. This results from the mortice not being cut correctly; and as you cannot, in this case, mark both sides and cut from both, as you did in making the towel-horse, this is not unlikely to happen. It will not, therefore, signify much if you purposely cut your mortices a little too long, and then, when you have placed the table on its legs, after gluing up the frame, and before it is dry, you can force it to stand truly, and then wedge up with glued wedges where necessary. You cannot, however, do this with the sides of your mortices, because you require these to fit exactly; you must therefore use extra care in keeping these as true as possible. In many cases you can wedge the ends of tenons to correct a bad fit, but never the sides. These are the probable, or I will say possible, faults against which to be on your guard.

Fig. 27.

In making a similar table with a drawer, the same operations have to be gone through, but the upper frame is somewhat differently constructed, and the corners of the drawer are united with dovetails. Plane up the legs as before, but cut mortices as at A. Fig. 27, which represents the right-hand hinder leg as you would see it standing in front of the table, and before the framework had been fitted in its place. B is the other hind leg, with the tenoned strips just ready to be driven in. The piece E is made as before, as is also C and its opposite piece at the ends of the table. But this pair of mortices, you see, are made shorter than before, and the strip C is notched at the bottom as well as at the top, forming a regular tenon, as it is called. Below this first is a second mortice, cut the other way, the longest side standing across the leg to receive a strip, D, upon which afterwards another strip, X, will be nailed or glued, forming the rebate in which the drawer will slide, and of which the upper surface must be level with that of the strip M. There is a plane for cutting out rebates without the necessity of adding a strip, but I do not suppose you as yet to have such a one. When these pieces, C and D, are driven up close into their places, they will touch along their sides, so that on the outside they will appear as one piece. Of course there will be a similar pair on the right-hand side of the table. D ought to be tenoned, so that the side on which X is to be nailed will lie flush or level with the corner of the leg, so that the strip X shall project wholly beyond it.

The left-hand front leg is shown at P, with its mortices, and the tenoned strips between which the front of the drawer will lie, closely fitting when shut. These front strips should be each 2 inches wide, the mortices 1 inch long, or as long as you can safely cut them; you must tenon the cross pieces, of course, to fit these.

All the rails may be of half-inch board. Mark all tenons across with the square as before, so as to give the exact inside dimensions, and you cannot well go wrong. These lines, too, will guide you in keeping the framework square and true; for if you have planed the legs correctly, and your strips are inserted exactly to the aforesaid lines, it stands to reason the work will be satisfactory. To make the drawer, observe, first, that it is not like a box as most boys would make it, for when turned upside down, as in Fig. 28, Fig. B, you will find the sides projecting beyond the bottom, which projections rest in the rebate, X, of the last figure, and take the whole weight of the drawer, enabling it to slide easily and smoothly in and out, especially if those surfaces which are in contact are rubbed with soap or blacklead, or a mixture of the two. At C you have a drawing of the same, with the bottom removed. This, you see, is a square or oblong frame dovetailed together, and when it is glued and dry, the bottom is slid in along the grooves in the sides (one of which is seen at x x), and a couple of brads driven through it into the back rail, K, fixes it completely. The front board of the drawer is cut and planed to fit exactly between the two rails which were morticed into the legs, as shown in the last fig., and is always of thicker stuff than the sides or bottom. It may, in the present case, be half-inch, and the rest quarter-inch.