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.
We have considered a few of the most important joints and splices used in the putting together of rough framing, and we will now take up some of the methods used in the joining together of finished work, where more care is necessary and where the joint or splice must very often be concealed from view. Much ingenuity has been exercised in devising some of these concealed joints, and great credit is due to the workmen, unfortunately unknown, who first invented them.
Fig. 66 shows the simplest kind of splice which can be used, similar in principle and construction to the butt joint already described. Here the pieces are simply planed off square and true on the ends and glued together with nothing but the glue to hold them. It is evidently not a very strong splice and should not be used where any tension or bending is likely to come at the point where the splice is made.
Fig. 67 shows a splice which is a slight advance over the simple butt splice. It is formed by ploughing the ends of the pieces to be spliced after they have been finished square and true, and inserting into the slot thus formed a third piece, which is called a "spline" or a "tongue." The spline is about 1 inch or less in width, and about 1/8 or 3/16 inch thick. Its length is regulated by the width of the pieces to be spliced together. As will be explained later, this form of connection is made use of in the construction of the better class of doors.
Fig. 67. Splice with Spline.
This form of splice is somewhat similar to the splice with splines, the difference being that only one of the pieces is ploughed, and the other is rabbeted on both sides so as to leave a projecting portion called a "tongue" which fits into the groove formed by ploughing the other piece and is fastened there securely with glue. The tongue should be about 3/8 inch thick, and should project about the same distance from the main body of the piece. The groove in the other piece must, of course, be of corresponding dimensions. The figures given are for l 1/8-inch stuff, which is the most common thickness of lumber used in cabinet work and interior finishing. For other thicknesses they should, of course, be varied. The tongued-and-grooved splice, Fig. 68, is used extensively in flooring.
Fig. 68. Tongued- and-Grooved Splice.
In Fig. 69 is shown what is known as a "rabbeted splice." It is similar to the halved splice described before but depends upon glue or small nails for its strength. It must be much more carefully made than the rough halved splice. As will be seen each piece is rabbeted on one side so that when put together they fit into each other perfectly. The tongue should here be about one half of the thickness of the piece and its projection from the main body of the piece should be about equal to its thickness. If this tongue is made too thin and projects too much, it is liable to curl up, as the wood shrinks in drying, and make ugly ridges on the finished work besides leaving the splice open.
Fig. 69. Rabbeted Splice.
A form of splice which is little used in this country, but which can occasionally be worked to advantage, is the filleted splice which is shown in Fig. 70. It is made by rabbeting the two pieces to be spliced, as in the case of the rabbeted splice, but this time both on the same side, and a third piece called a "fillet," which is somewhat like the spline in the splice with a spline, is inserted in the hollow space so as to join them together. This prevents any possibility of an open joint. The fillet is generally made somewhat less than one half the thickness of the pieces to be spliced, and is about 1 inch in width.
Fig. 70. Filleted Splice.
A variation of the filleted splice, which is quite generally made use of where great strength is not required and it is only necessary to cover up the butt splice neatly, is what is called a "battened splice," Fig. 71. As will be seen this consists simply in covering the butt splice with a small piece called a "batten." The batten should be about the same size as that given above for the size of the fillet, but can be made large or small as desired.
Fig. 71. Battened Splice.
A combination splice, which combines the advantages of the tongued-and-grooved and the rabbeted splices, is shown in Fig. 72. The groove is ploughed in the end of one piece and the tongue is left projecting on the end of the other piece while, in addition to this, one of the pieces is rabbeted against the other. The tongue should be about 3/8 inch thick and should project about the same amount from the end of the piece. One piece of the splice should be rabbeted against the other a distance of about 3/8 inch. This splice is considerably stronger than the simple tongued-and-grooved splice, but it is a great deal harder to make and is more expensive as regards both material and labor.
Fig. 72. Tongued- Grooved-and- Rabbeted Splice.
Another variation of the tongued-and-grooved splice consists in the introduction of a splay on one side of the tongue and a corresponding splay on one side of the groove so that they fit into each other. Fig. 73 shows this arrangement. It makes a very neat form of splice and it looks well, but it is apt to be less strong than the simple tongued-and-grooved splice and much weaker than the tongued-grooved-and-rabbeted splice, though stronger than the simple rabbet. This is, of course, a very troublesome and expensive form of splice to make, and it is, in consequence, seldom used.
Fig. 73. Tongued- Grooved-and- Splayed Splice.