This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
A joint in very common use in such situations as those which have just been mentioned is a development of the gained joint which is called the "tenon-and-tusk" or the "tusk-tenon" joint. This joint is shown in Fig. 45. The characteristic feature of this joint is to be found in the peculiar shape of the tenon which is cut in the end of one of the pieces to be joined, as shown in the figure. It may be seen that there is a small square tenon B cut in the extreme end of the piece, and that in addition to this there are other cuts C which constitute the "tusk." The bearing area is furnished partly by the under side of the tenon and partly by the under side of the tusk.
This joint makes a very good connection, and the cutting of the mortise does not weaken the piece of timber so much as does the mortise for a gained joint. It is especially applicable when it is desired to have the two pieces flush on top, although it may also be used in other positions. When the top of the tenoned piece must projed above the top of the mortised piece, the tenon may be cut as shown in Fig. 46.
Fig. 4.5. Tenon-and-Tusk Joint.
Fig. 4C. Tenon-and-Tusk Joint with Specially Cut Tenon Piece.
There are several ways of securing the tenon in place. The simplest is that shown in Fig. 47, where the pin B is passed through the tenon A and the mortised piece so as to hold the tenon securely in place. Another scheme is to cut the square tenon a little longer, as shown in Fig. 48, so as to pass clear through the mortised piece, and to fasten it with a peg B on the other side. The peg may be cut slightly tapering, as shown, so that when it is driven in place it will draw the pieces together. Still another plan is shown in Fig. 49. Here a small hole is cut in the header some distance back from the tenon and a nut C is placed in it, while a bolt B is passed through a hole bored lengthwise in the header to receive it. The bolt passes through the nut, which may be screwed up tight, thus drawing the pieces closely together and making the joint secure. In tightening this up, it is the bolt which must be turned, while the nut is held stationary inside of the square hole in which it is inserted and which is just large enough to receive the nut and a wrench.
Fig. 47. Pinned Tenon-and-Tusk.
Fig. 48. Pegged Tenon-and-Tusk Joint.