Hex nuts and bolts are some of the most ubiquitous and essential fasteners used in countless applications worldwide. From large-scale construction to precise machinery and everything in between, these fundamental threaded fasteners play a vital role.
Let’s explore what exactly hex nuts and bolts are, why they’re so popular, the various types and materials available, proper measuring and installation, and important safety considerations regarding these indispensable fastening components.
What Are Hex Nuts and Bolts?
Hex nuts and bolts are externally threaded fasteners, meaning the threads are on the outside surface. The most recognizable characteristic is their hexagonal shape, which allows for tightening and loosening with a wrench.
Hex Nuts
A hex nut is a small metal nut with internal threading that screws onto the external threads of a bolt to hold objects together. The six-sided hexagon shape allows for turning the nut easily with a wrench or socket. Hex nuts are commonly available in metric and imperial measurements.
Hex Bolts
A hex bolt is a threaded metal rod or shaft with a hexagonal head on one end that is driven through holes in workpieces and secured with a hex nut on the other side. The hex head, like with hex nuts, enables using a wrench or socket to tighten or loosen the bolt. Hex bolts come in many sizes and thread configurations.
Common Uses of Hex Nuts and Bolts
With their strong threaded grip and ease of tightening/loosening, hex nuts and bolts have become ubiquitous across many industries and applications.
Construction
In construction, hex bolts and nuts are essential for securing steel columns, beams, and girders. They also assemble the frames of heavy equipment and machinery on job sites.
Machinery
Nearly all machines rely extensively on hex fasteners to hold together casings and mounts for gears, pulleys, motors, presses, and more. Their versatility and strength make them ideal for precision machinery.
Automotive Industry
Automobiles are assembled with hex fasteners throughout the engine, drive train, chassis, interior, body panels, and more. Grade 8 hardened bolts often secure critical suspension and drivetrain components.
Types of Hex Nuts and Bolts
While sharing basic hexagonal and threaded attributes, hex nuts and bolts come in a variety of styles and designs for different applications.
Hex Nut Styles
Standard/Hex
The most common style is the standard or basic hex nut with chamfered ends for smooth threading. These are available from extremely small up to very large sizes.
Heavy Hex
Heavy hex nuts are thicker and wider than standard hex nuts, providing increased strength for use with large bolts and high torque applications.
Jam Nuts
Jam nuts are low profile thin hex nuts used to “jam” against another nut to prevent loosening from vibration.
Hex Bolt Styles
Hex Cap Screws
Hex cap screws have a hex bolthead with machine threads for use with a nut or tapped hole. The smooth shank allows close fitting through holes.
Carriage Bolts
Carriage bolts have a smooth, domed head without facets along with a square section under the head to prevent spinning when tightening a nut.
Elevator Bolts
Elevator bolts have a large, flat head with an internal socket drive for tightening without a wrench. The threaded end terminates in a hooked tip.
Hex Nut and Bolt Materials
Hex nuts and bolts come in a variety of metals and finishes for strength, corrosion resistance, temperature resistance, and appearance.
Steel
The most common and inexpensive option. Grade 2, 5, and 8 indicate increasing steel strength levels. Can be zinc plated for mild corrosion resistance.
Stainless Steel
For enhanced corrosion resistance in water, chemicals, and outdoor exposure. However, not as strong as hardened steel.
Other Metals
Brass, silicone bronze, and monel for specialized corrosion and temperature resistance. Titanium and alloy steel for very high strength.
Measuring and Specifying Hex Nuts and Bolts
Several key measurements must be properly specified when identifying the correct hex nut and bolt for an application.
Diameter
The nominal diameter of the threads, measured in millimeters or inches. Diameter also determines the hex size.
Thread Pitch
Threads per inch (imperial) or distance between threads (metric). Coarse and fine thread pitches are available. Must match between nut and bolt.
Length
Length of the threaded portion for bolts, overall length for hex cap screws. Ensure proper grip length for the application.
Proper Installation of Hex Nuts and Bolts
Installing hex nuts and bolts correctly is critical for maximum strength and safety.
Torque
Hex bolts must be tightened to the proper torque, especially for critical connections. Too little torque can loosen over time. Too much can overstress and break bolts.
Use of Washers
Washers evenly distribute load, reduce friction, and protect surfaces. Proper hardness washers must be used, especially with softer metals like aluminum.
Hex Nut and Bolt Safety
While providing strong and secure fastening, misuse of hex nuts and bolts can lead to failures and hazards.
Overtorquing
Applying excessive torque twists off bolts and damages parts. Use a calibrated torque wrench for critical bolts.
Corrosion
Rust and seizing can lead to broken bolts if forced. Use proper materials, lubrication, and maintenance to prevent corrosion.
Proper hex bolt and nut selection, installation, and maintenance are critical for creating safe, long-lasting, and functional bolted connections. While ubiquitous, these essential fasteners deserve care and respect.
FAQs
What are some other names for hex nuts and bolts?
Hex nuts may also be called six-sided nuts, hexagonal nuts, or externally threaded hex nuts. Hex bolts may be referred to as hex cap screws, hex head screws/bolts, or six-sided bolts.
What tools are used with hex nuts and bolts?
Common hand tools include adjustable wrenches, socket wrenches, nut drivers, hex keys, and torque wrenches. Power tools like impact wrenches and electric/pneumatic torque wrenches are used for efficiency.
How are stainless steel hex nuts and bolts different from standard steel?
Stainless steel resists rust and corrosion much better than standard steel, but is not as strong. Stainless steel nuts and bolts are recommended for exposure to water and chemicals.
What are some other head styles for hex bolts?
Button head, flat head, oval head, truss head, and socket head are other common hex bolt head variations beyond the standard hex head.
Why are properly hardened washers important?
Washers evenly distribute load, reduce friction, and protect softer surfaces from damage. Using washers with the proper hardness prevents embedding, deforming, and cracking under torque.
