Engineering:Sex bolt

Short description: Type of mating fastener

Sleeve nuts, one with mating bolt

A sex bolt is a type of mating fastener (nut) with a barrel-shaped flange and protruding boss that is internally threaded. The bolts sits within the components being fastened, and the flange provides the bearing surface. The sex bolt and accompanying machine screw sit flush on either side of the surfaces being fastened.

It is normally chosen because of its low profile compared to other nuts. The sex bolt often has a built-in feature, such as a slot, to aid in tightening the fastener. Some sex bolts, more commonly known as "architectural bolts", have knurled barrels to allow one-sided assembly.

The sex bolt consists of a female (internally) threaded barrel (nut) and a male (externally) threaded screw. Both the barrel and screw have heads designed to clamp (bind) material between the head of the barrel and the head of the screw, or to bridge the gap between two parts.

Other names for sex bolts include:

• architectural bolts,
• barrel bolts,
• barrel nuts,
• binding barrels,
• book screws or book binding screws,
• Chicago screws, or Chicago binding screws and posts,
• connector bolts,
• female screws,
• posts and screws or screws and posts,
• sleeve nuts,
• tower bust

Applications vary widely from book binding to installing bathroom partitions. This group of fasteners are used to assemble fitness apparatus, solar panels, playground equipment, railing systems, furniture, athletic helmets, knives, store fixtures, signs, panic bars, and many other products.

Technical guide to mating fasteners:

Barrel diameter

mating fasteners often are going through pre-drilled holes. The barrel diameter should be slightly less than the installation hole.

Barrel length

the barrel length is measured from underneath the head to the end of the barrel. Normally the length of the barrel is shorter than the thickness of the material being clamped. Another common term is "grip length", which is the thickness of the material that a mating bolt can effectively fasten or clamp.

Thread size

length and thread class fit for both barrel and screw. The more thread depth, the more difficult these parts are to manufacture, and the more expensive.

Head style

the most common head style for a mating fastener is a "truss" head. Other head styles are button, flat, grommet, hex head, large truss, low profile, oval, rivet and T-head.

Drive systems

mating fasteners are available in a variety of drives such as slotted, socket, Phillips, combination Phillips/slotted, as well as tamper-resistant drives: one way, 6-lobe with pin and drilled spanner.

Material and finish

mating fasteners are available in aluminium, steel, brass, copper, stainless steel and plastic materials. Barrels and screws are available anodized, zinc-plated, brass-plated, chrome-plated, bronze-plated, nickel-plated and black-oxide finish.