Screw Shackle Joint

This is similar to the joint of the same name described in the next section. It is used by the carpenter with tie-rods in strutting to floors, in composite timber and iron principals, centres, cofferdams, etc.

Serrated Joint

Serrated Joint is one with long indents or notches like the teeth of a saw, as represented in Fig. 55, and is sometimes used in scarfing and between the flitches of built beams, both straight and arched, to prevent the surfaces in contact from sliding. The different thicknesses, which have in some instances amounted to five or six or more layers of logs, partially interpenetrating each other throughout their length with serrated tabulations, are brought together by bolts and keys, but such an arrangement is safer for resisting a longitudinal than a cross stress, owing to the peril involved by the timber splitting across the serratures when strained by the latter description of force.

Ship Lapping Joint

This is synonymous with halved joint.

Shouldered Joint occurs between two timbers when one is strengthened by being shouldered or thickened out to reinforce its abutting or resisting powers. Figs. 43 and 47 respectively show a mortise and tenon thus treated. The queen-post is often shouldered by cutting a notch to take the end of the straining beam, and the principal rafter is by some carpenters considered to be shouldered when a notch about 2 in. deep and 1 in. wide is taken out of it on both sides to give a bearing to the notched down purlin.

Socket Joint occurs in roofs, centres, cofferdams, and other heavy work, and is formed by inserting the tenons, ends, or other parts of two or more timbers or pieces exposed to a tensile or transverse strain into an iron receptacle shaped to receive them, and which is called a socket or socket piece. It is most frequently made of wrought iron, though it is sometimes cast, especially when employed as a "head." On the contrary, shoes which take the feet of timbers exposed to compressive strain are usually of cast iron. One of its commonest positions is at the apex of rafters, in which situation it is called a head, and is shown in Fig. 56, where a socket unites a king-rod, ridge-piece, and rafters, instead of framing the two latter into a timber post. Fig. 57 illustrates another one uniting a straining-beam, rafter, and queen-rod concentrated together, as usual in a truss, at the same point of support. Besides serving such purposes, a socket is useful in protecting the ends of timbers from damp or fire, and projections or cavities are easily cast or wrought upon it at any part to give support to cross timbers or other parts clustering around it.

Ship Lapping Joint 56

Fig. 55.

Ship Lapping Joint 57

Fig. 56.

Spiked Joint

This is one fastened with one or more spikes, which are large wrought nails varying from 4 in. to 14 in. in length. They are used for securing timbers to plates, shores or props to curbs, fender-pieces to wal-ings, walings to piles, struts to posts, planks to beams, and, in fact, in most of the multitudinous descriptions of heavy carpenter's work.