Strap and Cotter Joint

Strap and Cotter Joint is one strengthened with a strap, admitting of adjustment by means of wedges or keys, commonly called cotters, described under Cottered Joint, and which pass through slots in its turned-up ends, by which arrangement the effects of settlement or shrinkage may be partially counteracted. Sometimes only one cotter is thought sufficient to draw up the strap and the timber or element it grasps.

Strut Joint, as its name implies, is one between a strut and some other piece, and admits of different forms, the object being to obtain a uniform distribution of stress or an equality of bearing upon the whole of each surface in contact. If the beam is horizontal and fixed at one end only, a well-fitting joggle joint will answer; but if both ends are supported, the struts should, if possible, butt and mitre against a straining piece bolted to some part or other of the beam, as in Fig. 63. When the end of a strut is inserted so that it offers an angular rest, the consequences of splitting must be provided for, if the direction of the fibres appears to favour such a mishap.

Swallow-Tail Joint

This is the Continental name for the dovetail, which, however, is occasionally so called in the United Kingdom. For instance, in dovetailing a joist to the depth of about in. down upon a wall plate, the resulting joint is often called a swallow-tail.

Swallow Tail Joint 64

Fig. 63.

Tabled Joint

The projecting surfaces of scarfs running in the direction of the grain are called tables, and the junction of two opposite and corresponding ones forms this joint.

Tabled, Indented, and Keyed Joint is a form of scarfing:, of which common and useful varieties for resisting tension are illustrated in Figs. 64 and 65. On each bevelled or notched surface, as the case may be, an indent and a projection called a table are formed side by side, which respectively fit the corresponding and opposite table and indent in the other. Between the two tables, in a hole left for the purpose, folding and very slightly tapering wedges or keys of hard wood are driven in just sufficiently tight to bring the bearing surfaces well up together, which being done, the joint is secured with straps driven well home, or bolts and plates tightly screwed up, the latter being preferable to washers for preventing injury to the fibres.

Tie Joint

Tie Joint is one formed to resist a tensile stress, and amongst other positions, is found at the junction of a tie with timbers inclined to one another in order to retain them at a fixed inclination, or, in other words, to prevent them from spreading. It usually takes the form of a double notch slightly dovetailed (see Carpenter's Boast), as shown in Fig. 66, which must be spiked or pinned. Very frequently, when occurring between heavy timbers, iron bolts, sometimes jagged, or tough oak treenails, are useful to strengthen it against drawing. Wales or waling pieces are bolted to guide piles, and secured with nuts and large washers. Pile foundations to cast iron sewer pipes, etc, are tied together by the cap-sills, cross-heads, or bearers, which are either similarly bolted thereto with inch screw bolts, or bolted and checked. Iron straps bolted to timber, and having projecting cork-ings protected against oxidation, are built into masonry, and securely hold the two together.

Tie Joint 65

Fig. 64.

Tie Joint 66

Fig. 65.

Tie Joint 67

Fig. 66.