of each part, and a hardwood key, (in the form of the letter I) connects the two together. Scribing is the cutting, out of the face of one moulding, a hole of the contour of another to form a joint. It is chiefly used in joints of sashbars, internal angles of moulded skirtings, etc., and really is a moulded mortise cut into another moulding to receive a moulded tenon of the same section as the mortise, but in a converse form. For instance, in Fig. 223, it will be noticed that on FIG. 225 FIG. 226 A a moulded mortise or notching is cut out, with the ovolo hollow, as it were; and on B, which we will call the tenon, the cutting has the ovolo convex or projecting to fit and fill up the hollow on A. FIG. 227 A scribed housing is a housing made to the contour of the moulding it is going to receive (Fig. 224). FIG. 228 FIG. 229 FIG. 230 Chamfering is the taking off of the arris or sharp edge of an angle, as Fig. 225, the angular groove formed by the meeting of two chamfered angles (Fig. 226) being called a V-joint. Match Boarding.-This is an arrangement of boards matched and put together with grooved and tongued joints, and their edges "shot" or planed truly, so that a fine joint can be made. Match boarding, otherwise called cleating, is of several kinds, the chief of which are: Plain matched boards (Fig. 227). Beaded-one-side match boarding (Fig. 228). Joints, Straps, and Other Fastenings We have already described the principal joints used in ordinary framing. There are also a considerable number of joints in which advantage is taken of special mechanical aids, either in the way of cutting the joint so as to give a special arrangement of bearing surfaces, or by special devices such as straps, bolts, etc., to strengthen the joint. Joints should be formed in such a manner that the bearing parts may have the greatest possible amount of effective surface. For should that part of the joint which receives the strain be narrow and thin, it will indent itself into the pieces to which it is joined or become crippled by the strain, producing in either case a change in the form of the framing. The effect of the shrinkage and expansion of timber should also be considered in the construction of joints. On account of the shrinkage of timber, dovetail joints should seldom be used, as the smallest shrinking allows the joint to draw out of its place; they can be used with success only when the shrinkages of the parts counteract each other-a case which seldom happens in carpentry, though very common in joinery and cabinet-making. |