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fitted, so as to produce the greatest strength with the least possible waste of material; or how to proportion a joint, so that it shall not fail or give way before another. In too many instances, the method of joining woodwork is regulated by no other rule than the fancy of the workman. It is not difficult to explain why joiners' work so frequently fails; why the parts separate with a trifling strain; or, from being bound too tightly together, fly and split in all directions. It is not so frequently from the bad execution of the work, as from the want of an adequate estimate of the strength required to resist the stress on the joint. We shall, then, describe the several kinds of joints, or the methods of framing and joining timber; and, under each head, give such directions, founded on the principles of mechanics, as will enable the workman to proceed with some degree of certainty; and not, as is too frequently the case with artisans, observe no other rules than those which custom has authorized, and practice made familiar.

Dovetailing.

We have given, in the cuts, several examples of dovetailing. The parts which fit into each other are known by different names; the projecting piece, represented in fig. 20, is called the pin of the dovetail; and the aperture into which it is fitted, as shown in fig.

21, is called the socket. Now the strength of a dovetail depends upon so proportioning the pin and the socket as to enable them to support, rather than destroy, each other. Let A B CD, fig. 20, be a scantling, which is required to be joined to another, by means of a single dovetail. The strength of the joint depends on the form of the dovetail, as well as on the proportion it bears to the parts cut away. We shall endeavor to lay down the principle on which the greatest strength may be secured. Having squared the end of the scantling, and gauged it to the required thickness, AIKLM, divide IM into three equal parts, at K and L. Let KL be the small end of the dovetail, and make the angles IK G and M L H equal to about 75 and 80 degrees respectively; and make GE and HF parallel to AN and B O. Then cut away the parts A I K G E N, and B MLH FO, and having formed the socket to correspond, by

marking the form of the dovetail on the top of the piece A B C D, fig. 21, and cutting away accordingly, the pieces may be fitted together, as shown in fig. 22. It may be here observed, that the bevel of the dovetail, that is, the angle

Fig. 22.

IKG, fig. 20, may be either more or less than has been mentioned, according to the texture of the wood. Hard, close-grained woods, not apt to rive or split, will admit of a greater bevel than those which are soft, or subject to split; thus the bevel of a dovetail in deal must be less than in hard oak, or in mahogany. It is a great fault to make a dovetail too beveling, for instead of adding to the strength of the joint, as some persons suppose, it weakens it; for provided the bevel is sufficient to prevent the possibility of pulling the pieces apart, the less the bevel that is given the better. It must have been observed, that there is a great difference between the dovetail made by the cabinet-maker and by the joiner; the former has very little bevel, the latter very much; the former looks neat, and is at the same time strong; while the latter, appearing to aim at strength, looks clumsy, and is at the same time much the weaker of the two.

Fig. 23 represents the dovetail in common use for drawer-fronts. When it is required to hide the appearance of the joint in front, the board ABCD is cut with the pin, and A EFB with the socket. The pins in this sort of dovetail are in general from about three quarters of an inch to an inch apart, according to the size of the pieces to be joined.

Fig. 24 represents the pin part of a lap dovetail, which, when put together, shows only a joint, as if the pieces were rebated together, as shown in fig. 25. ABCD represents the pin, EFGH the socket, and when put together the line H G is only seen as a joint; and if the corner AB is rounded to the joint GH, it will appear as if only mitred together. This kind of dovetail is very useful for many purposes where neatness is required, such as in making boxes.

Fig. 26 represents a still neater dovetail; and, as the edges are mitred together, it is termed a mitred dovetail; and is the same as that shown in fig. 6, except that instead of the square shoulder, or rebat, in A B, it is cut into a mitre, and the other piece is made to correspond.

Another very neat as well as expeditious method of joining pieces of wood, and it is somewhat analogous to dovetailing, is shown in fig. 27. The joint is first formed into a mitre, and the pieces are then keyed together, either by making a saw kerf in a slanting direction, as at AB, or by cutting out a piece, as at CD, in the form of a dovetail. The first method, A B, is called, amongst workmen, keying together; the second, CD, key-dovetailing.

The last method to be mentioned is that shown in fig. 28, and may be termed mitre dovetail grooving; the part A B being formed with shoulders cut to the required bevel, and a piece left for the pin dovetail, which is inserted into the socket dovetail, made to correspond to it in the piece CD, which has been previously formed into a mitre. This method, though not much employed, may be used with great advantage in many instances, particularly when it is required to join pieces together the lengthway of the grain.

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Mortice and Tenon.

Under this head, we shall endeavor to give some rules necessary to be observed in attempting to proportion the parts of the mortice and tenon, so that they may be equally strong, or that the tenon may not be more likely to give way than the checks of the mortice; for this is the principal thing to be avoided. The workman

frequently allows too little substance for the tenon, lest he should weaken the mortice; and sometimes he falls into the opposite error; facts which clearly prove that he is not acquainted with a means of obtaining a maximum of strength with a given quantity of material.

Figs. 29 and 30 represent a simple mortice and tenon. The dotted

Fig. 29.

Fig. 30.

To show the thickness of the

Fig. 31.

lines show the parts to be cut away. tenon, and consequently the width of the mortice, we have here one tenon and two shoulders, that is, three parts; one of which is to be allowed for the tenon, and two for the shoulders; and this will in general be found the best proportion, for if the tenon be more than that, it will weaken the shoulders of the mortice. Now if we have, as is frequently the case, two tenons in one piece, as represented in fig. 31, there will be five parts, two tenons, and three shoulders; so that each tenon will be one fifth of the thickness of the stuff, for the shoulders are all equal to the tenons. This rule may be generally observed, unless the tenon is at a considerable distance from the end of the stuff, and then something more may be allowed for its thickness, as the mortice is then not so liable to split; but it should in no case, however sound the timber, or tough the material, be more than two out of four parts; that is to say, it can never be safe to make the tenon more than half the thickness of the stuff, and that only under particular circumstances, when the mortice is near the middle of the scantling, for the piece in which the mortice is cut would, in other cases, be considerably weakened. There is frequently in joiners' work a shoulder at the bottom of the tenon that fits into the piece in which the mortice is cut, as represented in fig. 32; and the tenon is divided into two parts, as there shown, which, when the stuff is wide, is a good method, as it strengthens the piece in which the mortice is cut, without weakening, in the same proportion, the mortice itself; and we would suggest, in this case, that the piece BC, cut out from between the tenons AB

--B

Fig. 32..

and D C, be nearly, if not quite, one third of the distance AD; for if much less, the piece left between the mortice will add but very little to the strength of the piece in which the mortice is made; and the tenon would be stronger in proportion to the mortice-piece than necessary. It may be here observed, that if the width of the tenon be much more than four times its thickness, additional strength will be gained by dividing the tenons into two or more parts, as shown in the figure, particularly if we allow a small piece at the bottom of the tenon, as represented in the drawing.

Grooving and Lapping.

This method of joining wood-work is analogous to that of morticing and tenoning. When it is required to join two boards together by means of a tongue and groove, the groove should never exceed one third of the thickness; and often, if the piece for the tongue be formed of hard wood and liable to split, one quarter of the thickness will be sufficient. When a panel is let into a groove in the style, the joiner is often guided by the thickness of the panel itself, which should never be less than one third the thickness of the style.

In making a groove across the grain, as for partitions, it will be best, in most cases, to make it about a fifth or sixth of the substance of the stuff. But, if the groove be formed into a dovetail, one quarter the thickness will be better, and the dovetail should be made a little tapering, but not too much. It should, in fact, be so made as to go almost home without requiring a blow from a hammer or mallet to drive it into its place until it has nearly attained it; and all joints should be easily separated with a gentle blow before they are glued. In a lap-joint, that is, in lapping two pieces together, supposing them of equal thickness, half the substance of each should be cut away; and, if of unequal thickness, the lap should be made in the thinner piece, of about two thirds or three quarters of its thickness, according to the substance of the thicker piece; thus endeavoring in this, as in all other cases, to avoid weakening one piece more than another.

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Bending and Gluing-up.

In bending and gluing-up stuff for sweep-work, much judgment is necessary, and, as the methods are various, we shall mention a few which the workman may apply, as occasion may require, one method being preferable to another, according to the nature of the work in hand.

The first and most simple method is that of sawing kerfs or notches on one side of the board, thereby giving it liberty to bend in that direction; but this method, though very ready and useful for many purposes, weakens the work, and may cause it to break when strains are thrown on the piece. But a tolerably strong sweep may be made in this manner, if, after sawing the kerfs