The Essential Guide
to Lockbolts

Learn the two types of lockbolts, understand their benefits and multiple applications, as well as top brands and installation tools.

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Lockbolts are versatile fasteners that are widely used in manufacturing and construction. They are easy to install and deliver superior joint strength because they will not loosen with time and are extremely resistant to heavy vibrations.

Like a conventional nut and bolt, the lockbolt consists of two pieces: a pin and a locking collar. However, whereas conventional nuts and bolts require access to both sides of a joint in order to install the bolt head and the nut, lockbolts are installed using installation tooling that requires no complex tightening or torque measuring.

To install a lockbolt, the pin is positioned on one side of the joint and the collar on the other. Using a lockbolt tool, the pin is pulled to bring the joint together so the head of the pin is flush on the back side, and then the collar is swaged for a tight fit on the front side where the tool is applied. The tool pulls on the pin, which locks the collar into the grooves of the pin—i.e., swages the collar—and the result is a firm, lasting connection. Unlike other threaded fasteners, the lockbolt does not require a lock washer to create a secure joint.

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Chapter 1

Two Lockbolt Categories

There are two basic types of lockbolts: those utilizing separating pintails and those that do not.

Lockbolts utilizing separating pintails are designed to shear the pin off near the collar once installation is complete. The lockbolt is designed with a breakpoint in the pin so the tail readily separates once the collar is swaged and the spent pintail is either ejected or collected in a container on the installation tool. To define the breakpoint, the pintail is made narrower to ensure a clean break. Some lockbolts have a multi-grip design in order to accommodate a wider range of acceptable material thickness, thereby reducing the number of different length sizes required to keep in inventory. The pintail grooves are designed to separate at a wider range of workplace thickness. The advantage of a multi-grip lockbolt is that one multi-grip lockbolt can be used in place of several lengths of conventional lockbolts.

Lockbolts without separating pintails do not have a breakpoint in the pin, so the pin remains intact after installation. Depending on the application, lockbolts without separating pintails have two distinct advantages:

  1. There is no spent extra pintail that needs to be collected after installation is complete.
  2. There is no shock and loud break-off sound when the pintail separates, which reduces noise and cuts down on operator fatigue.

Additionally, the reduction in installation recoil shock greatly improves the life of the installation equipment.


Chapter 2

The Unique Benefits of Lockbolts

Because of their superior performance under stress and vibration, lockbolts have become standard fasteners in multiple industries
for a variety of applications. Lockbolts offer numerous unique characteristics.

Lockbolts are stronger than screw joints or rivets. Once installed, they provide a permanent joint that cannot be removed without special tools. This makes them lasting and tamperproof.

For applications that require joints to withstand continuous vibration, such as with factory machinery, construction tools, mining tools, and transportation applications, lockbolts will outlast other types of fasteners. The swaged collar forms a permanent bond with the grooves of the bolt pin that can’t shake loose. In fact, lockbolts are stronger and more durable than rivets, welds, adhesives,
or other conventional fastening systems, and they are easier to install.

Lockbolts also outperform torqued bolts in both shear strength and tensile strength, including offering a longer fatigue life. When a lockbolt is installed, the pin is placed with the head on one side and the pin is pulled from the opposite side to bring the materials together. As the pin is pulled, pressure is placed on the collar, forcing the softer collar into the grooves of the pin’s harder material. The squeezing action not only reduces the diameter of the collar but also increases its length and stretches the pin to generate more force over the joint. The shear strength of the lockbolt is the result of the material strength and diameter of the lockbolt; the stronger the material and the wider the diameter, the higher the shear strength. The tensile strength of the lockbolt is the product of the shear resistance of the collar and the number of grooves the collar fills.

For manufacturing and construction applications, lockbolts often are preferred over traditional bolts because they reduce labor and installation costs. Installation is fast and easy—simply set the bolt, fit the collar, and tighten. Anyone can install a lockbolt, which eliminates the need for specialized training such as that required for certified welders. You can train anyone to install lockbolts in a matter of minutes. And lockbolts take only a few seconds to install—a fraction of the time needed for a conventional nut and bolt.

Lockbolts also are easier to visually inspect to see if they are secure. The Huck BobTail® and Huck-Spin® 2, for example, feature tabs on their collars to quickly verify that installation is correct.

Chapter 3

Applications for Lockbolts

As with most types of fasteners, lockbolts come in a wide range of sizes, lengths, materials, and designs suitable for almost any application.

Because of their resistance to vibration and high shear and tensile strength, lockbolts have come into common use for the most grueling applications. Here are just a few areas where lockbolts are common:

  • Transportation, such as buses, mass transit vehicles, trucks, and railway cars

  • Automotive applications, such as recreational vehicles, trailers, and automobiles

  • Aerospace manufacturing, including planes and airport equipment

  • White goods, such as lighting, food services equipment, medical equipment; and alternative energy hardware, such as solar systems and wind energy turbines

  • Assembly applications, such as building warehouse shelving or working within automated systems used by large manufacturers and distributors

  • Agricultural equipment, construction equipment, and recycling equipment

  • Metal fabrication and power plant systems

  • Bridge and tunnel structures

Lockbolts can be used wherever there is a need for joint integrity and lasting construction. Lockbolts have been proven to be extremely reliable and can withstand extreme loads and vibrations. In many cases, the joint is stronger than the material being joined, and using lockbolts makes joint installation fast, easy, and foolproof.

Chapter 4

The Leading Lockbolt Makers

There are a variety of lockbolt manufacturers and lockbolt types, but the two most recognized brands are Huck® and Avdel®.

Huck is a subsidiary of Arconic Fastening Systems and offers a variety of fasteners called HuckBolts® in small and large diameters for moderate and heavy-duty applications. Huck lockbolts are made from aluminum, steel, and stainless steel, and can be used for most applications.

Avdel, which is part of STANLEY Engineered Fastening, is one of the oldest manufacturers of fasteners, including lockbolts. The company was originally formed as Aviation Developments in 1936 and developed a new type of speed fastener for the aviation industry when airplanes began to be made of aluminum. Today, Avdel manufactures a wide range of rivets, blind bolts, and lockbolts for virtually any application.

Both manufacturers offer lockbolts with and without separating pintails:

Huck Lockbolts Utilizing Separating Pintails:

Huck C6LC6L® - The Huck C6L is the original HuckBolt and has been manufactured for more than 50 years. This six-groove lockbolt is designed to deliver superior, lasting performance, including reduced costs for reworks and warranties, and can be installed quickly with little or no training. The C6L is available in aluminum, steel, and stainless steel in diameters ranging from 3/16 inches to 3/8 inches with either round, truss, flush, or rivet heads.

Huck C50LC50L® - The C50L HuckBolt is designed for heavy-duty applications and is available in diameters from 1/2 inch to 1-3/8 inches. They have been tested to exceed the torque and shear strength of conventional bolts and are available with standard, flanged, and low-profile collar types. Made from carbon steel, they also are available with round, flush, stainless steel, truss, large truss, or threaded heads.

Huck Magna GripMagna-Grip® - The Huck Magna-Grip is available in diameters from 3/16 to 3/8 inches for moderate and heavy-duty applications. It offers a wide grip range so you can use one lockbolt to connect materials of different thicknesses for various applications. Magna-Grips can be easily installed in seconds (up to 1,200 lockbolts per hour, according to Huck) and the pins break off flush with the collar every time for a cleaner finish. The Magna-Grip is available with a button, truss, broad truss, flush, or rivet head.

Avdel Lockbolts Utilizing Separating Pintails:

Avdel AvdelokAvdelok® - The Avdelok is a high-strength lockbolt that offers high shear strength and is highly vibration-resistant. The Avdelok is available in sizes ranging from 3/16 inches to 3/8 inches in aluminum, steel, and stainless steel. It also has full, half, and flanged collar options and comes with either a brazier, countersunk, truss, or large head.

Avdel Avdelok XTAvdelok XT® - For especially heavy-duty applications, such as construction, mining, bridge-building, and railway manufacturing, the Avdelok XT family of lockbolts are large diameter two-piece steel fasteners measuring from 1/2 inch to 1-1/8 inches. They are available with full or flanged collars and round or large truss heads.

Avdel MaxlokMaxlok® - The Maxlok is a multi-grip lockbolt with high strength and vibration resistance. It is suitable for multiple application thicknesses, so you only have to stock one bolt. The Maxlok is available in aluminum or steel in diameters from 3/16 to 1/4 inches, with brazier, mushroom, truss, or countersunk heads.

Huck Lockbolts Without Separating Pintails:

Huck BobTailBobTail - The Huck BobTail has a unique design with no pintail and shallower threads to spread out the service load and increase load strength. The BobTail is designed for fast installation with one pull of the tool’s trigger to engage and eject the bolt pin. The BobTail is available in a range of standard and metric diameters and is available with round, truss, flanged, flush, or cap heads.

Huck HuckSpin 2HuckSpin 2 - The HuckSpin 2 is designed for fast and easy installation and longer tool life with less wear on the head and lower hydraulic pressure. It also features a high clamp load—up to eight times that of a nut and bolt—and is easy to inspect at a glance. The HuckSpin 2 is available in 1/2-, 5/8-, and 3/4-inch diameters, as well as M12, M14, M16, and M20 diameters, and offered in black chromate or zinc plate finish.

Avdel Lockbolts Without Separating Pintails:

Avdel NeoBoltNeoBolt® - The Avdel NeoBolt is a pintail lockbolt with a non-breaking stem and annular locking grooves for heavy-vibration, heavy-duty applications such as commercial vehicles, mining equipment, or construction equipment. The NeoBolt is available in diameters from 3/16 inches to 1 inch and made of medium- or low-carbon steel with either a clear zinc or black oxide pin and zinc-plated flanged collar. It comes in various sizes for lasting, vibration-resistant performance.

Chapter 5

Installing a Lockbolt

Although lockbolts are available in various sizes, designs, and materials, the lockbolt installation process is the same for all lockbolts.

First, the lockbolt pin is placed in a pre-drilled hole with the head on one side and the collar placed over the pin on the other side. The lockbolt tool is then placed over the fastener pintail. When activated, the lockbolt tool pulls the pin up, cinching the head on the far side and bringing the material together to form the initial joint. Installation is completed when the tool anvil presses the collar downward, applying pressure so the collar presses against the pin and swages the collar, forming a tight fit between the collar and the threads of the pin. When the tool releases the lockbolt, it breaks off the pintail (or releases the pin if the pintail is to remain intact), and installation is complete.

Every lockbolt is designed with a collar that is made of a softer material than the pin, so when the collar is swaged, it is tightly pressed into the grooves of the pin. The more metal-to-metal contact, the stronger the joint, and the less prone it will be to loosen with vibration.

There are a few important considerations to ensure that the lockbolt is properly installed and will provide a strong, lasting joint. The objective is to create a joint that has little or no movement to minimize metal fatigue. In fact, lockbolts tend to have shallower threads than conventional bolts, so there is more metal and a closer fit between the collar and the grooves to increase fatigue strength. The diameter of the hole also is a factor. The tighter the fit in the hole, the less movement in the joint, which increases joint strength and longevity.

You also want to match the power of the swaging tool to the lockbolt. Matching the torque of the tool to the tensile strength of the collar gives you an optimal connection. If the torque is too low, the connection may be loose; if the torque is too high, it could strip the lockbolt. You also want to be sure the swaging tool has little or no lateral motion.

To ensure you use the right tool for the lockbolt, it’s important to understand the various types of tools available.

Manual Lockbolt Installation Tools

For smaller lockbolts that carry less of a load, you often can use hand-operated lockbolt tools. There are a number of manual swaging tools that are typically used for simple jobs or for repairs.

One of the most popular manual lockbolt tools is the Marson® Big Daddy® Huck Tool. Designed specifically for 3/16- or 1/4-inch Huck Magna-Lok®, Magna-Tite®, and Magna-Grip fasteners, the Big Daddy has self-adjusting two-piece jaws to grasp the pin and extra-long handles to provide extra leverage. It’s ideal for truck and automotive bodies, floor structures, storage compartments, and other applications where hand-installed lockbolts are used.

Pneudraulic Lockbolt Installation Tools

For production volume lockbolt installations or larger bolts that need more powerful tools, pneudraulic tools are a good choice. Both Huck and Avdel have pneudraulic installation tools that are suitable for heavy- duty installations.

The Huck Model 2025 is designed for 3/16- and 1/4-inch diameter lockbolts and the Huck Model 256 will handle lockbolt diameters of 3/16-, 1/4-, 5/16-, and 3/8-inch. These tools are ergonomically designed for ongoing use with less operator fatigue and have separate vacuum pintail collection systems available. The 2025 is relatively lightweight at 5-7 pounds and delivers a pull capacity of 5,280 pounds at 90 psi of air. The Model 256 is more powerful, weighing in at 11 pounds and delivering 9,986 pounds of pull at 90 psi.

The Avdel ProSet® XT pneudraulic installation tool also is well-suited to production installation applications. The strongest tool of the ProSet series is the ProSet XT4, a lightweight yet study tool that delivers the highest pull force in the range. It is innovatively designed with a left or right and on/off swivel air fitting, which gives the operator additional flexibility while conserving energy.

The Avdel 73200-02000 is a hydro- pneumatic installation tool made for placing Avdel lockbolts up to 3/8 inches. It features a high pull force and long stroke, delivering 8,138 pounds at 80 psi and weighing 10 pounds for heavy-duty installations. It has an aerospace-grade aluminum alloy head and handle that make it lightweight yet durable. The 73200-02000 model is ergonomically designed to reduce shock loading during use and increase time before re-priming. Avdel offers a number of nose assemblies that can be used with this tool.

Hydraulic Lockbolt System Tools

For factory installations and applications where you need durable tools for ongoing use, both Huck and Avdel offer hydraulic system tools. These systems consist of interdependent parts, such as hoses, hydraulic pumps, and accessories that work together to deliver optimal lockbolt installation performance.

Huck Hydraulic Tools

For Huck lockbolts, Arconic offers a variety of hydraulic installation tools.

The SFBTT8 is the Swage Forward BobTail Tool, designed to install 1/4-inch, 5/16-inch, and 3/8-inch fasteners such as the BobTail. It is lighter and more compact than previous units, making it ideal for use in tight spaces. Similarly, the SF20 Swage Forward BobTail Tool works with 1/2-inch and 5/8-inch lockbolts with a 2-inch stroke; the SF32 works with 3/4-inch BobTails with a 2-inch stroke; and the SF46 works with 7/8-inch to 1-inch BobTails with a 2.5-inch stroke.

If you need a lightweight tool, the Huck 2480 weighs 2.21 pounds and offers high-speed installation of a variety of HuckBolts. The Model 2581 is a lightweight tool with a pull capacity of 10,700 pounds, and it has one moving part, which means more reliability and less maintenance. (Models 2582 and 2583 add an eccentric piston for better center-to-edge measurement, and the 2583 offers a longer stroke.)

For large-diameter HuckBolts, the Model 3585 is ideal for C50L and BobTails, and the 3585PT can be used for BobTail and HuckSpin lockbolts.

To round out its hydraulic lockbolt tool systems, Huck also offers various Powerig® hydraulic power sources and accessories.

The Model 940 Powerig is a portable hydraulic power unit with 120V or 220V AC electrical power designed for production and field use; it’s easy to transport with simple hydraulic outlets and couplers. The Model 913F Powerig is a portable gasoline-powered hydraulic power unit for use in the field where a power source is unavailable. It weighs 175 pounds when full of hydraulic fluid. The Model 918 and 918-5 are the largest hydraulic Powerigs available for high-production applications. The Model 918 can power two tools at a time and the 918-5 can power three hydraulic tools. These are electrical units that can generate enough pressure to power installation tools up to 100 feet away. Of course, Huck also offers a complete line of replacement hydraulic hoses, gauges, nose assemblies, and accessories to complete its hydraulic systems.

Avdel Hydraulic Tools

Avdel also offers a wide range of lockbolt tools, each with unique specifications for different lockbolts and applications.

The Avdel 7287 has a lightweight head to install NeoBolts (3/8 inches), Avdeloks (up to 3/8 inches), and other fasteners. It has a wide variety of interchangeable nose assemblies and can be fitted with a collar cropper to cut and remove lockbolts. It also has a remote intensifier which is mounted on casters to make it more portable.

Avdel’s 734 AVTM of tools can set all Avdelok and Avdelok XT lockbolts from 3/8 inches to 1-1/8 inches, as well as 1/2-inch to 1-inch NeoBolts and 5/16-inch to 5/8-inch Avbolts. These hydraulic tools are built to last with easy-to-change nose assemblies and hoses.

The AV series is powered by Avdel’s Enerpac® PRO Series pumps. These are high-efficiency pumps designed to run cooler with 18 percent less current, providing an outstanding power-to-
weight ratio and low-voltage operating characteristics. Of course, Avdel offers a variety of nose assemblies to accommodate different lockbolts, hoses, pressure setting gauges, and other accessories.

Huck Cordless Tools

Huck also introduced a line of cordless range-force lockbolt tools in partnership with Makita, a proven leader in industrial cordless tools. The Huck BV4500-118K2 is a robust tool that accepts the same nose assemblies used on the Huck 2025 pneudraulic tool. They have an electronically adjustable pull that pulls up to 4,500 pounds; the BV2200 model can pull up to 2,200 pounds. These tools are beneficial for their portability and versatility on the job.

Chapter 6

Understanding the Best Way to Purchase Lockbolts

If you are sourcing lockbolts and blind bolts, it pays to read the available technical literature and learn the specifics about lockbolt product categories and part numbers.

Bay Supply has a complete library of specification sheets, catalogs, and parts literature that can get you started. Bay Supply engineers also are available to train distributors and other professionals, helping them understand lockbolt categories, how to identify the right fasteners, and what to look for in terms of diameters, grip range, materials, plating, and installation equipment.

To accurately specify the right lockbolt for any task, you need to understand the associated measurements and application parameters, such as:

  • Pre-drilled hole size

  • Material thickness and its relationship to “grip range”

  • Requirements regarding shear and tensile strength

  • Vibration resistance

  • Corrosion resistance

  • General suitability for specific applications and end use requirements

For example, the most commonly used lockbolts are the Magna-Grip and C6L series in 3/16-inch, 1/4-inch, and 3/8-inch diameters. For sizes larger than 3/8 inches, a BobTail is recommended for most applications as the most efficient option. There are some applications that typically call for a specific fastener, such as a Huck- Spin 2, though, in some cases, a BobTail or some other lockbolt product will have the same appearance and deliver the same performance once it is installed.

The more you know about lockbolts, their composition, and their applications, the easier it will be to match the right lockbolt and installation tools to the job. To learn more about lockbolts, blind bolts, and other fasteners, contact the experts at Bay Supply. We are always here to help.

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