TIMBER CONNECTORS

Figure 1-26.—Scabs. Figure 1-27.—Split ring and split-ring joints. washers under both the bolt head and the nut. The bolts are then tightened until the washers bite well into the wood to compensate for future shrinkage. Bolts should be spaced a minimum of 9 inches on center and should be no closer than 2 1/2 inches to the edge or 7 inches to the end of the timber. Driftbolts, also called driftpins, are used primarily to prevent timbers from moving laterally in relation to each other, rather than to resist pulling apart. They are used more in dock and trestle work than in trusses and building frames. A driftbolt is a long, threadless rod that is driven through a hole bored through the member and into the abutting member. The hole is bored slightly Figure 1-28.—Shear plate and shear-plate joints. smaller than the bolt diameter and about 3 inches shorter than the bolt length. Driftbolts are from 1/2 to 1 inch in diameter and 18 to 26 inches long. Butt joints are customarily connected using driftbolts; however, another method of making butt-joint connections is to use a scab. A scab is a short length of timber that is spiked or bolted to the adjoining members, as shown in figure 1-26. TIMBER CONNECTORS A timber connector is any device used to increase the strength and rigidity of bolted lap joints between heavy timbers. For example, the split ring (fig. 1-27) is embedded in a circular groove. These grooves are cut with a special bit in the faces of the timbers that are to be joined. Split rings come in diameters of 2 1/2 and 4 inches. The 2 1/2-inch ring requires a 1/2-inch bolt, and the 4-inch ring uses a 3/4-inch bolt. Shear plates are shown in figure 1-28. These connectors are intended for wood-to-steel connections, as shown in view B. But when used in pairs, they may 1-15