IEC used the October 2008 Fastening & Assembly Solutions Exhibition to unveil a new patented self-locking and reusable threaded fastener. Known as the SBS (Secure Bolt System) Fastener, the design comes in two styles, one of which has the added advantage of being tamper-resistant. This combination of reusability, self-locking capability and tamper resistance is believed by IEC to be unique.
When tested by accredited test laboratories worldwide, the SBS fastener was found to perform better than conical washers, and was vastly superior to threaded fasteners with flat washers. For applications where vibration-induced loss of torque is a problem - or must be avoided - then the SBS is worth considering. Likewise, the fasteners are suitable for applications where thermal cycling is anticipated.
How the SBS fastener works
The SBS fastener features a bolt head (or nut) with ramps formed in the underside. A hexagonal washer with ramps of the same angle is installed beneath the bolt head such that the two sets of ramps face each other. Using a standard spanner (wrench) or socket, the bolt is tightened to the required torque, with the spanner simultaneously turning the hexagonal washer. Once the required torque is achieved, the spanner is used to turn the bolt head a fraction of a turn further to ensure that the steps between the ramps on the bolt head and washer come into contact. Small radial 'teeth' on the underside ensure that the washer achieves a firm grip on the underlying material.
Because the ramps (cams) on the bolt head and washer are at a slightly greater angle than the thread angle, the fastener locks itself together rather than loosening under the influence of vibration.
If the fastener needs to be removed, this is easily achieved using a standard spanner or socket on the bolt and washer together.
The tamper-resistant SBS fastener is similar in concept but uses a round washer with ramps, rather than the hexagonal washer of the standard SBS fastener. In this case, however, a special socket is required, with small protrusions that correspond with notches in the edge of the washer.
Installation remains quick and straightforward, but removal is all but impossible without the special socket. Of course, removal is achieved easily with the aid of the special socket.
Both metric and SAE (UNC) sizes are available in the form of both nuts and bolts. Different grades and classes, as well as customised designs, can be manufactured to order. Standard products cover M6 to M24 bolts (M6 to M20 nuts) and 1/4inch 20 UNC to 5/8inch 11 UNC bolts (1/4inch 20 UNC to 1/2inch 13 UNC bolts). Standard materials are high-tensile steel and 316 stainless steel. High-tensile fasteners are zinc-plated as standard, though nickel plating is available as an option.