Lockbolts are the preferred fastener for tough environments because, once installed, they won’t loosen, even under the toughest conditions such as continuous stress or vibration. The two-piece lockbolt consists of a grooved pin and a sleeve, and once installation is complete, the sleeve is permanently fixed so it can only be removed with a special cutting tool.In fact, a lockbolt is stronger than a conventional nut and bolt with a lock washer, a rivet, or a weld. However, as with all fasteners, the lockbolt can deliver peak performance only if it is properly installed.
A lockbolt has a locking collar or nut and is difficult to remove once installed. However, for proper lockbolt installation, you need a special tool. Depending on the application, you can use a hydraulic, pneumatic, handheld, or cordless tool, but the installation needs to be snug with no play in the bind in order to last.
The Basics of Lockbolt Installation
Lockbolt installation is relatively simple. A pin is placed through the pre-drilled holes to join two pieces of material. The pin has a head chosen to suit the application, such as a rounded head, countersunk head, or extra wide head for softer material to prevent pull-through. Once in position, the collar is fitted over the pin, ready to tighten.
To tighten a lockbolt, you use a tool that fits over the collar and compresses it against the pin. The lockbolt tool is designed to swage the collar against the bolt, compressing the collar onto the grooves of the bolt for maximum metal-to-metal contact so there is no play and no possibility of the fastener loosening over time. As the tool swages the collar, it pulls the pin up, which compresses the materials being joined while pressing the collar into the joint for a tight fit.
Lockbolts typically come in two basic types: those with pintails that separate off when placed, and those where the pintail remains as part of the bolted assembly after installation. The most common type is a lockbolt where the pintail separates off the assembly upon installation. As the lockbolt tool is used to complete its swaging of the lockbolt collar, the installer cuts the lockbolt pin so it is flush with the collar. This makes for a neat and lasting joint. There are installations in which removing the pintail isn’t necessary, so it is left intact after installation.
Installation Using a Lockbolt Tool
Choosing the right lockbolt tools is essential if you want to ensure proper installation. You need to make sure you have sufficient pull strength to create a tight joint and sufficient pressure to properly compress the collar. If you have too little power, the collar won’t make a tight joint; too much pressure and you could damage the joint or the collar.
A lockbolt tool goes through three stages during installation:
- First, the tool applies a pre-load. This is the initial stage when the tool grasps the pin and pulls on the pintail. The tool pulls on the pin so that on the blind side of the joint, the side opposite the exposed pin, the two pieces of material are tightly drawn together.
- Following the pre-load, the lockbolt tool is forced down on the collar. Because the collar is made of softer material than the pin, this forces the collar to fill the grooves of the harder pin to create the joint. As the tool pulls, it stretches the pin, which strengthens the clamp force. This completes the actual fastener joint.
- The final step shears the pin off at the collar, if using the style of lockbolt where the pintail separates on installation. The discarded pin either drops to the floor or is collected using a device attached to the lockbolt tool. If the pintail remains as part of the bolted assembly, the tool nose unclamps off the pintail and the resulting swaged collar tightly clamps onto the fastened lockbolt pin. With this type of lockbolt, you can check that the collar is properly swaged by viewing the inspection marks imparted by the tool nose as it separates from the installed collar.
Types of Lockbolt Tools
Hydraulic lockbolt installations are typically used for heavy-duty applications, such as in a factory or anywhere you need a tool that delivers reliable service all day, every day. Leading lockbolt makers Huck and Avdel both offer hydraulic tools, including all the interdependent parts, such as hoses, hydraulic pumps, and accessories. Hydraulic lockbolt tools are available to handle different sizes and types of bolts with pull strengths up to 10,000 pounds. These tools are often used in factories to build mining equipment and heavy-duty machinery.
Huck and Avdel also make pneudraulic lockbolt tools for heavy-duty installations, such as the Huck 2025, Huck 256, the Avdel ProSet® XT, and Avdel 73200-02000. These tools are smaller and lighter, weighing only a few pounds to about 10 pounds, which makes them easier to use for long periods. They typically have a pull strength of 1,400 pounds and up, depending on the air pressure. These types of tools are popular for field applications, such as construction, bridge building, boat manufacturing, and aircraft manufacturing.
There also are manual lockbolt manual swaging tools, which are typically used for simpler operations such as repairs. One of the most popular is the Marson® Big Daddy® Huck Tool, a self-adjusting tool for the for 3/16- or 1/4-inch Huck Magna-Lok®, Magna-Tite®, and Magna-Grip® fasteners. This type of tool is commonly used for applications, such as truck or auto body repair.
Recently, Huck 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.
Bay Supply carries a complete range of lockbolts and lockbolt tools for every application. If you are trying to figure out which lockbolt or tool to use, contact one of our fastener professionals to learn more.