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.
The simplest splices are those intended to resist compression alone, and of these the most simple is that shown in Fig. 54. This piece is said to be "fished"; the two parts are merely sawed off square and the ends placed together. A couple of short pieces A-A, called "fish plates," are nailed on opposite sides to keep the parts in line. In the splice shown in Fig. 54, the splicing pieces are of wood, and ordinary nails are used to fasten them in place, but in more important work thin iron plates are used, the thickness being varied to suit the conditions. They are held in place by means of bolts with washers and nuts.
If for any reason it is desired not to use plates of this kind, four small pieces called dowels may be used, as indicated in Fig. 55. These dowels may be set into the sides of the timbers to be spliced, so that they do not project at all beyond the faces of these pieces and a very neat job may thus be obtained.
It is but a step to pass from this simple splice to the "halved" splice shown in Fig. 56. It will be noticed that it is much like the halved joint described above, the only difference being that the pieces are continuous, instead of being perpendicular to each other. The nature of the splice will be easily understood from the figure without further explanation. A modification of this which is somewhat more effective, is shown in Fig. 57. The cuts are here made on a bevel in such a way that the parts fit accurately when placed together, and the splice is called a "beveled" splice.
Fig. 53. Dovetail Halved Joint with One Flare.
Fig. 54. Fished Splice.
Fig. 55. Doweled Splice.
Fig. 56. Halved Splice.
The halved splice is perhaps the best that can be used to resist direct compression, and when it is combined with fish plates and bolts, as shown in Fig. 58, it may be used in cases where some tension is to be expected. It will be noticed that in Fig. 58 the ends of the timbers are cut with a small additional tongue A, but this does not materially strengthen the splice and it adds considerably to the labor of forming it. In general it may be said that the simplest splice is the most effective.
Fig. 57. Beveled Splice.
Fig. 58. Halved Splice with Fish Plates and Bolts.
Whenever the pieces are cut to fit into one another, as they do in the halved and beveled splices, the splice is known as a "scarf" splice, and the operation of cutting and joining the parts is called "scarfing." Scarf splices are used, as we have already seen, both alone and in combination with fish plates. The fished splice is always the stronger, but the splice where scarfing alone is resorted to has the neatest appearance.