Bolt (fastener)

A bolt is an externally helical threaded fastener capable of being tightened or released by a twisting force (torque) to a matching nut.

In 1851 the Great Exhibition of the Works of Industry of All Nations was to be held in Hyde Park, London, England, and it was decided to build the Crystal Palace as part; this had to be done in 190 days, and at reasonable cost.

The construction firm responsible, Fox Henderson, decided to use nuts and bolts, but to use standardised sizes, a revolutionary method at the time.

The use of interchangeable nuts and bolts was so successful that the Whitworth standard was widely adopted.

The academic distinction, per Machinery's Handbook,[3] is in their intended purpose: bolts are designed to pass through an unthreaded hole in a component and be fastened with the aid of a nut.

For this reason, many bolts have a plain unthreaded shank (called the grip length), as this makes for a better, stronger dowel.

The presence of the unthreaded shank has often been given as characteristic of bolts vs. screws,[4][verification needed] but this is incidental to its use, rather than defining.

These modern designs span a large range of sizes and can carry a considerable torque.

Slip is prevented through friction of the "faying" surface, that is the plane of shear for the bolt and where two members make contact.

Because friction is proportional to the normal force, connections must be sized with bolts numerous and large enough to provide the required load capacity.

Common bearing type connections include: shear tabs, beam supports, gusset plates in trusses.