Many styles of expansion bolts are now manufactured under various patents, and these may be procured in all sizes and made of iron, steel, or brass.
In [Fig. 7] are shown several makes of expansion bolts. The McCabe expansion bolt, shown at (a), is constructed of a malleable, cylindrical-shaped, slotted case, or shell, a, the aperture of which reduces in size and engages with a bevel-shaped hexagon nut b. By turning the bolt, the nut is drawn toward the head and thus expands the outer case in its passage; this in turn binds against the sides of the hole in the masonry into which the bolt is inserted. The shell, as the outside case a is called, can be procured in any length or diameter, and can be used with any machine bolt having a standard thread. The McCabe bolt is suitable for bolting any thickness of material, provided the proper length of bolt is employed.
The Brohard expansion bolt shown at (b), performs the same functions as the bolt illustrated at (a). The case, or shell, a, is composed of two or more parts riveted to a wrought circular plate, near the head, as at b. These several parts are expanded by means of the beveled nut, which approaches the head as the bolt is turned. The principal feature of the Brohard expansion bolt is that the beveled nut c cannot be forced from the case on account of the lug d, which is attached to the nut and travels in the slot e when the bolt is turned.
Fig. 7
The Steward and Romaine double-expansion bolt is shown at (c). The shell of this bolt is composed of two semicylindrical parts, as at a, a, that are somewhat longer in diameter than the wedge-shaped nut and the sleeve at b and c, respectively. Each half of the shell is held in place by light rubber bands. The wedge-shaped parts are caused to approach each other by the turning of the bolt, and thereby expand the split case at both ends simultaneously. From the fact that this bolt is expanded at both ends, it is called a double-expansion bolt, although it may be made single-expansion by omitting the wedge-shaped sleeve at the head.
Fig. 8
The Star expansion bolt, shown in [Fig. 8 (a)], performs exactly the same duty as other expansion bolts, but its construction is radically different. This bolt consists of only two parts, called shields. Each shield is semicircular in form and interlocks at the joints. The exterior of these shields has four rows of corrugated ridges, or star-shaped projections, that prevent the shields from turning in the hole. The interior of the shell is threaded and decreases in size toward the farther end. Thus, by inserting a lag, or coach, screw of any length, so as to engage with the thread, the shields are spread apart at the farther end while the screw is entering the aperture.
The Diamond expansion bolt shown at (b) is practically the same as the one just described, as will be observed from the figure.