Fasteners are among the oldest inventions of man, going back, at the very least, to ancient Egypt. Today, the term “fastener” covers many hardware devices, such as nails, screws, pegs, clamps, anchors pins and industrial bolts.

The last of these, industrial bolts, are a type of threaded fastener, made with external helical, or male, threads, also called ridges. Industrial bolts, which are made from rods, also feature a top portion, called a head. Compatible with high pressure drills, handheld screwdrivers, and allen wrenches alike, they are used to hold together industrial materials in industries such as at-home and commercial building construction, aircraft building, automotive manufacturing, and military vehicles and equipment.

Industrial bolts are made in a number of different ways, and vary by head type, pitch measurement, and the major diameter of their external thread. Bolt heads are classified by their shape and size. Some common head types include: binding heads, flat heads, oval heads, pan heads, taper heads, and truss heads. The pitch is a measure of the root, which is distance between separate thread crests. (Crests are another name for ridges.) This is measured along the thread axis using a tool called a thread pitch gauge.

Diameters are understood based on the helix angle, which is the measured angle of the threads, which will either go up to the right or up to the left, and the thread angle, which is a measured, v-shaped angle between the crests. Read More…

Leading Manufacturers

DAN-LOC Bolt & Gasket

Houston, TX | 800-231-6355

Ford Fasteners, Inc.

Hackensack, NJ | 800-736-5014

Ken Forging

Jefferson, OH | 888-536-3674

Bolts are also often named for their use, shape, or size. Examples of these type of bolts include: anchor bolts, expansion bolts, eye bolts, hex bolts, J bolts, lag bolts, shoulder bolts, stud bolts, and U bolts.

J bolts and U bolts are both named after the letter of the alphabet they most closely resemble.

Anchor bolts are used to anchor supports to a foundation. Examples of items they are used with include street signs, columns, and traffic sign posts.

Expansion bolts are used to enable expandable features of certain seating and flooring, such as those found in theaters, auditoriums and lecture halls. Composed of a nut, metal cone, lead sleeve, and taper head, they are specifically named after their attachments, which expand as the bolt is forced into a surface.

Like J bolts and U bolts, eye bolts are also named after their shape. Threaded at one end, they are named after the circular eye that sits at the other end in place of a head.

The “hex” in hex bolts stands for hexagon, referencing the six-sided, hexagonal head of this extremely common bolt.

Lag bolts are named after their function: they “lag” together wooden beams or posts and serve other carpentry duties. The use of the word “lag” in this context comes from the early use of these bolts, when they fastened items they called lags, which primarily referred to the vertical wooden posts of buildings, barrels, casks, and the like. Lag bolts, which either have a hexagonal or a square head, are made of wood.

Shoulder bolts are named after their shafts, which are nicknamed as shoulders. This is because their pivot mounting shafts, which are not threaded all the way to the top, but instead stop before the head, are smooth-sided and slightly wider than the threaded area. Shoulder bolts, which may have a round or square head, are typically made from stainless steel.

Finally, stud bolts are round metal bars, made from long, threaded rods known as studs. They are either completely covered or covered at the ends in threads.

Standard bolts are made from materials like stainless steel, aluminum, and titanium. However, while these strong, durable metals work for most bolts, sometimes an application calls for more than that. In particular, this is the case with those bolts designed to work in the military and aircraft industries. In these industries, bolts must, at the very least, meet specific standards that match the gravity and sensitivity of the applications they serve. Usually, these bolts must also be made with special, anti-corrosive materials, receive strengthening and protective coatings and undergo rigorous quality testing.

Either way, the bolt fabrication process begins when a manufacturer selects his or her preferred material, always in the form a wire rod. After this, the rod is placed in a furnace for thirty hours, then immersed in a bath of sulfuric acid, which removes all potential rust particles. To disallow the resurgence of rust, a manufacturer will then coat the wire rod in a phosphate that doubles as a lubricant. Next, the rod must be shaped. This is done via the metal forming process known as cold forging.

Cold forging involves forming a raw metal into a new shape using high pressure, room temperature heat, and pre-formed, rod-shaped dies. The metal is squeezed through and between two dies until it takes their shape. Once shaped, the newly formed rods are cut into smaller pieces and sent through another die that will form their heads. Finally, to add threads, manufacturers press thread patterns into the bolt at room temperature with high pressure rollers. This method is called rolling.

To learn what bolts will best serve their application, or how to fabricate the most durable bolts, interested parties should contact an experienced industrial bolt manufacturer or supplier.

Bolt Informational Video