JOINTS AND SPLICES IN CARPENTRY Before beginning a description of the framing, it will be well to consider the methods employed in joining pieces of timber together. The number of different kinds of connections is really very small, and the principles upon which they are based may be mastered very quickly.
All connections between pieces of timber may be classified as joints or as splices. By a "splice" we mean a connection between two pieces which extend in the same direction, as shown in Fig. 36, and each one of which is merely a continuation of the other. The only reason for the existence of such a connection is the fact that sticks of timber can be obtained only in limited lengths and must, therefore, very often be pieced. By a "joint" we mean any connec tion between two pieces which come together at an angle, as shown in Fig. 37, and which are, therefore, not continuous. Such a connection may be required in a great many places, and especially at the corners of a building.
Joints. The principal kinds of joints to be met with in car pentry are the "butt joint," the "mortise-and-tenon joint," the "gained joint," the "halved joint," the "tenon-and-tusk joint," and the "double-tenon joint." But Joint. This is the most simple of all the joints, and is made by merely placing the two pieces together with the end of one piece against the side of the other and nailing them firmly to each other, after both have been trimmed square and true. Such a joint is shown in Fig. :38. The two pieces are perpendicular to each other and neither piece is cut. The nails are driven diagonally through both pieces, an operation which is known as "toe-nailing" and are driven home, if necessary, with a nail set. This is called a "square" butt joint. Fig. 39 shows two pieces which are not perpendicular to each other. They are trimmed to fit closely together, and are then nailed in place. Such a joint is called an "oblique" butt joint. The butt joint does not make a strong connection between the pieces, and should not be used if much strength is required. It depends entirely upon the nails for its strength, and these are very likely to pull out.
This form of joint is sometimes modified by cutting away a part of one of the pieces, so that the other may set down into it as shown in Fig. 40, the square joint at A, and the oblique joint at B.
This gives much additional strength to the joint, especially in the case shown at B, where there may be a tendency for one piece to slide along the other.
Mortise-and-Tenon Joint. From the modified butt joint it is only a step to the "mortise-and-tenon" joint, which is formed by cutting a hole called a "mortise" in one of the pieces of timber, to receive a pro jection called a "tenon" which is cut on the end of the other piece. This arrange ment is shown in Fig. 41. The mortise is shown at A, and the tenon is shown at B. It will be noticed that there is a hole bored through the tenon at C, and that another hole is bored in the mortised piece at B. These holes are so placed that when the pieces are joined together, a wood pin may be driven through both holes, thus preventing the tenon from being with drawn from the mortise. The pin should always be inserted in a mortise-and-tenon joint. Ordinarily this pin is of hard wood, even when the pieces to be joined together are themselves of soft wood, and it may be of any desired size. Round pins from 4 inch to I inch in diameter are ordinarily employed, although it may sometimes be found better to use a square pin.
The form of mortise-and-tenon joint described above may be used wherever the pieces arc perpendicular to each other. When, however, the pieces are inclined to each other, a modification of the above joint known as the "bridge" or "straddle" joint is employed. This joint is shown in Figs. 42 and 43. It is similar to the square mortise-and-tenon joint, having a similar mortise and tenon, but these are cut in a slightly different way. In Fig. 42 the tenon A is cut in the end of the inclined piece and fits into the mortise B cut in the other piece. In Fig. 43 the mortise A is cut in the end of the inclined piece and the tenon B is cut in the other piece.