Читать книгу The Young Mechanic - James Lukin - Страница 8

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The previous chapters were devoted to such exceedingly simple and easy specimens of carpentry as can be made by any boy of eleven or twelve years of age, or even younger, who has the necessary perseverance, and will take sufficient care in measuring and fitting. In both and all similar cases, it is better for such to buy pieces of board already planed, and of nearly the desired size; but I shall no longer presuppose such necessity, but advance the young mechanic to the dignity of a plane, and a few more of the more necessary and useful tools. The list may therefore now comprise—

1 Hand Saw, 16 inches or so in length, a full-sized one being almost beyond the powers of a boy.

3 Firmer Chisels, quarter, half, and one inch wide.

1 Mallet.—Chisel handles should never be struck with a hammer, which splits the handles.

1 Hammer.—This should be light. The best way is to buy a hammer-head, and make the handle. A heavy one can be added, but will hardly be required at first, and is useless for light work.

1 Jack Plane, 1 Smoothing Do.—The jack plane is not usually added to a boy’s tool-chest, but it is impossible to plane up a long straight edge without it; and as these planes can be had from 12 inches in length, I should certainly recommend one, say 12 to 15 inches.

3 Gimlets, 3 Bradawls.—One of each of these should be as small as can be obtained. Add a medium and a larger one.

1 Screwdriver, 1 Pincers, 1 Cutting Pliers.—Screwdriver should be of a medium size; the pliers such as are used by bellhangers.

1 Compasses.—These should be light carpenter’s compasses, not such as are made of brass and steel. They are very useful.

2 Gouges.—Carpenter’s gouges, not turner’s. They will answer for the present, in many cases, to make round holes in boards. The centrebits and braces are expensive.

1 Oil-stone.—There is a cheap and quick-cutting stone called Nova Scotia which will answer the purpose well.

Mortice-gauge.—The use of this will be shown presently.

1 Square, 1 2-Foot Rule, Glue Pot, and Brush.—These are, as before stated, indispensable. The rule need not have a brass slide; the square may be made entirely of wood, or with a metal blade 6 to 9 inches in length.

The above, with the addition of a carpenter’s brace and bit, two or three augers, about three mortice chisels, and a hatchet, would suffice for a very large amount of good work. Indeed, it represents almost a complete set of tools, the only additional ones that are at all likely to be needed being a longer (trying) plane, rebate plane, and pair of match, or tongue and groove planes. Without any of the latter, the young carpenter will find it easy to carry out a good many light specimens of his ingenuity.

It is much better, in general, to work with a few tools, and contrive to make them answer all sorts of purposes, than to lay in a larger and more expensive set at starting, for the latter are sure to be abused and kept in bad order, because if one chisel gets blunt, another is taken up, instead of sharpening the first; and planes and other tools are treated in a similar manner, and a carelessness is engendered fatal to success. It is astonishing how much may be done with few and inefficient tools, but then the utmost patience and industry have to be exercised, much as we see prevailing among the native workmen of India and America, who execute the most beautiful and delicate work with tools which, in the hands of a European, would be generally simply useless.

The next work that should be attempted by the young mechanic should be mortice and tenon jointing, as used in constructing frames of various kinds for doors, window-sashes, tables, and other articles of everyday use. Perhaps one of the simplest and easiest examples will be a towel-horse, which, at any rate, will be of use when completed.

Now, it may be at once stated, that for work of this kind especially, but generally also for all work, it is essential to be able to square up truly the several pieces required. This will require practice—long and careful practice—and the beginner will meet here with his first and chief difficulty, but he must not despair.

Fig. 15.

It has been presupposed that a strong work-bench, table-plank mounted upon trestles, or some sort of tolerably efficient and firm bench has been obtained, or is accessible, and, in addition, a strong stool upon which to saw, cut out mortices, and so forth. A small carpenter’s bench, with a wooden vice, is most handy and serviceable, but is not absolutely necessary. It will be easy to make one by and by; for the present, any available substitute must be used. The height of the proposed towel-rail may equal the length. About 2 feet 6 inches will be a fair size, and it may be of the simplest possible form, such as is here delineated (Fig. 15). The upright sides may be made of strips of pine, one inch wide and three-quarters of an inch thick—the rails 1¼ wide and three eighths of an inch thick. The feet will be considered presently. If careful attention is given to the following directions, not only will the result be certainly satisfactory, but the way will be paved for the workmanlike construction of a great number of similarly useful articles.

The size of the rough material must always be greater than that ultimately needed, to allow of the necessary waste in sawing and planing. Pine boards, however, are usually cut of certain general widths and thicknesses; and although we have here set down stuff of one inch by three-quarters, it may be cut from inch board, because very little will be wasted by the plane, and the finished work will be sufficiently near to the above measure for the intended purpose, one-sixteenth of an inch or so being of no practical importance in the construction of such an article as a towel-rail. Get, therefore, from the carpenter, a strip of pine 1 inch wide and 6 feet in length, cut from a board 1 inch thick, and also a strip for the rails (of which there will be three), 4 inches wide and 2 feet 9 inches long, cut from a half-inch board. The rails you are to saw yourself from the latter strip, which will give you practice in sawing a straight course, and the work is easy in half-inch stuff. You may therefore begin by cutting these, for which purpose you will want guide-lines dividing the strip into three of equal width. There is a very simple way of marking these by means of a chalk line, which I will here describe.

The width of the board I set down at 4 inches, because the rails, when finished, will be 1¼ inches each, or, in all, 3¾ inches. As each contains eight eighths, as already explained, 4 inches will contain thirty-two eighths. Dividing by 3, we shall have ten eighths for each strip, or 1¼ inches, and two eighths, or a quarter of an inch, to spare for waste. Take the compasses, therefore, and open them to 1¼ and a little over (rather less than to the next division on the rule), and take it off at each end of the board (Fig 16, A B).

Fig. 16.

Take off, again, from this to mark the width of the next strip, and the board will be divided with sufficient accuracy for our present purpose. Take a piece of twine, long enough to stretch from end to end of the plank, and something over, and tie a knot at one end. Stick a bradawl through the string, close to this knot and into the board, as seen at C of the same figure. Take a lump of chalk, and chalk the line from end to end. Then strain it down the board, holding it by the left hand, so that it is stretched from one mark to the other, where the saw-cut is to be made. With the finger and thumb of the other hand, raise it a little in the middle, and let it suddenly go, when it will make a perfectly clear and straight line upon the board. Make a similar and parallel line for the next saw-cut. In the present case, you need not mind cutting this chalk mark out. Try and saw right down, so as to split it.

Fig. 17.

You now have your strips cut out, but they require to be planed. You might, indeed, with advantage, have planed the whole strip on both sides before marking and cutting it, but it is equally easy to do it afterwards. The jack plane is the one to be used for this purpose. I must suppose it to be sharp and in good order; if not, ask some carpenter to set it for you for the present, but I will soon tell you how to do it for yourself. Indeed, you will have to learn how to sharpen all your tools before you can be called a good workman. If the plane is properly set, the cutting edge will project very slightly only from the bottom; so that when held as in Fig. 17, and the eye directed along the sole, only a narrow shining slip of metal will appear. If too far out, it will hitch and make bad work; if not far enough, it will not cut at all; but the common fault of beginners is to have it too far out, because from their imperfect handling of this tool they often fail to make it cut, when in the hands of a carpenter it would work well. Now, if the iron projects too far, hold it as shown, so that you look along the sole, and give it a tap with your wooden mallet on the upper face at A, and this is also the way to loosen the wedge and irons for removal. By a blow at B, you can send the cutting edge forward to cut more deeply, or in this case you may tap the iron itself with a metal hammer, but tapping the end of the wood is better.

To plane the edges of these strips, you ought to have a bench with a vice, but there are ways and means to do without it, and one is so good that I shall speak of it here, although it necessitates a somewhat abrupt break-off in my description of the towel-rail. It is a kind of vice that is fixed to a board which is laid upon the work-bench when required.

Fig. 18.

In Fig. 18 is a drawing of one of two kinds of such vices which I will explain. This first consists of two pieces of wood (ash will be better than pine) about 9 inches long and 2 inches thick. They are cut in the shape given in the drawing, and screwed to the board, not tightly, but so as to move freely upon the screws. The board should be an inch thick to give the screws a firm hold. You can see by the figure that the tails of the pieces cross each other sometimes when in use. To allow of this, they are cut like B and C, so that one can go inside the other. Now, if you consider a little, you will understand that if we stand a strip of board between the two, and push it forward against the insides of the tails of these curiously-shaped blocks, it will make the opposite knobbed ends close nearer together, and these will grip the piece of wood, and the harder we push it forward, the more closely it will be gripped and held; but the moment we draw back the piece, the two jaws will open to let it go free. You can try first of all upon a thin piece, which can be shaped by your knife, and make a model of this vice, and then if you can’t manage to cut out such a one of thick wood, the carpenter would do it for you, and it will be handy for many purposes. If you have nothing of this kind, nor a vice to your bench, drive in two pins or pegs of wood, or two nails, a little way apart, so as to allow your strip of wood to stand upon edge between them, and drive two more a little way from these; then one at the end to form a planing stop. A tap at the sides of these nails will cause them to hold the strip edgewise, quite well enough to allow you to plane it. There are other ways, and I shall describe them by and by. In the meantime use nails, or any other plan that will answer.

Fig. 19.

Fig. 20.

I shall suppose, therefore, that one of the narrow strips is thus set on edge upon your bench ready to be planed. Grasp the handle of your plane firmly with the right hand, and lay hold of it in front of the iron with the left. Draw it back, and then send it steadily forward, pressing it downwards at the same time. Now the advantage of a long plane is, that it does not descend into the hollows of the work, but rests upon the projections, as in Fig. 19, A. A short plane would do as seen at B, and therefore would never make a long straight edge. You have two special points here to attend to. You have to plane a level line from end to end, and also keep the edges square to the sides, which is by no means easy at first. You must keep trying it with your square, as I have shown you in Fig. 20, and not rest satisfied until the handle fits close to the side of the strip, and the edge lies also close upon that of the strip anywhere along its length. I daresay you will think this of no importance in such a common thing as a pine towel-horse; but I may tell you this is the very secret of carpenter’s work, and when you can saw and plane truly, and work “to square,” you can make almost anything. It is true that the strips for the rails are not of great importance in this case, but the upright side pieces are, and if these are out of truth, the holes cut through them for the rails, which are called mortices, will be out of truth also, and you will see the towel-horse, when it is made, all twisted and awry, and nothing you can do will make it stand firm or look well. It is, in short, no use to pretend to learn carpentry unless you at once make up your mind to succeed, and therefore you must always use the square and try your work as you go on. All the difference between the usual work of carpenters, and that of boys or men who do not know how to work, consists of the squareness and good fit of what the former make. Boys never seem to trouble themselves about such things, and so you see their boxes and rabbit-hutches look twisted, and being badly fitted, they soon go to pieces.

Having planed up the sides and edges of the rails as square and true as you can, cut the other long strip in half, and square up this also, taking care that both pieces are alike and both truly worked. If your bench is sufficiently long to take the whole strip, plane it up before you cut it across, and you will be sure to have the sides of your towel-rail equal in size. You have now to make your first essay in cutting mortices. Follow these directions, and you will not fail. I shall not limit the description to these special mortices, but give you general directions.

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).

If a workman has to cut many mortices on pieces of the same size, he frequently constructs a rough mortice gauge with double points, which marks both sides of the mortice at once, like K. A fixed block at K, the right distance from the points, l m, of two nails, is sufficient when all the mortices are to be alike. There is, however, a regular double-pointed gauge, made generally of ebony, plated with brass, and a brass rule to which one of the points is fixed, and which is acted on by a screw at the end, which can be turned by the thumb and finger. This has the effect of separating or closing the two points according to the desired width of the mortice, its distance from the side of the piece being regulated as before by the sliding head fixed by a wedge. This is an expensive tool, and need not be purchased. There are also, let me add, many costly tools of various forms and uses; but let the boy’s motto (and man’s, too, for all that) be, “Do as well as you can without.” You have no idea how a little ingenuity and contrivance will save your pockets, and that, too, without in the least tending to spoil your work. All you require are a few of the most generally useful tools in first-rate condition—chisels, saws, and planes, sharp and well set, and fit for work at any moment.

With regard to uniting two pieces of wood or other material with glue, it must be remembered that if you use this substance in a thick semifluid state, and in quantity, its effect will be lost. Make it a rule to put on as thin a coat as possible, and let it be not thicker than cream, so that it will freely flow into corners, and spread evenly over the surfaces to be united. Make the wood also quite warm, so that the glue shall not be suddenly chilled, and let it be used boiling. Always heat it either in a proper glue-pot, or at any rate, place the vessel which contains it (a small gallipot, for instance) inside another vessel in which water can be kept boiling.

The glue, which should be thin and transparent, being broken into small pieces, should be put into such a vessel as suggested, and covered with cold water, and it should be allowed to remain thus until swollen and softened. Then bring the water in the outer vessel to the boiling point, and do not use the glue until it is entirely dissolved and of one uniform consistence. It should be stirred while boiling with a piece of stick, and a brush used to lay it upon the pieces to be joined. It very generally happens that pieces glued by boys fall apart almost directly. This is almost entirely due to the fact that the glue is used thick and clotty, and in too great quantity, while the wood is never made warm as it should be. If two pieces are properly joined in this way, it is almost impossible to separate them at the joint—the wood itself will give way and split before the glue will yield to the strain. Carpenters use various forms of clamps or vices to hold work together until the glue shall be dry; but for boys by far the best plan, where any such holdfast is needed, is to bind the parts together with twine, and then to set them aside for twelve hours at least. It is seldom that articles once united by glue and separated will unite firmly a second time.