Lockbolts have become one of the most popular types of fasteners for manufacturing, construction, transportation, mining, and a variety of other applications. There are many benefits of lockbolts, and they have proven to be a durable and lasting fastener solution in most applications.What makes the lockbolt so durable is its design. The lockbolt was developed more than 70 years ago by Louis C. Huck as a commission for the U.S. Navy and railcar manufacturers. These manufacturers needed a fastener that could create a lasting joint that would resist loosening with constant vibration. Conventional nuts and bolts continued to exhibit flaws in stressful applications, loosening under vibration and weakening over time. Huck’s lockbolt design solved those problems.
Lockbolts have a unique locking system that defies vibration and extends its useful life. The secret: The lockbolt has a larger cross-sectional connection area between collar and pin with no stress concentrations, such as those associated with nuts and bolts.
Where nuts and bolts use a threaded screw to form the joint, lockbolts use a smooth-bore collar that is fitted over a threaded bolt. When tightened, the collar is pressed into special locking grooves on the bolt. The result allows bonding across a larger surface area, creating a locking, vibration-resistant joint.
To install a lockbolt, the collar is fitted over the pin and permanently swaged. The lockbolt pin is positioned in a pre-drilled hole to connect two pieces of material and, using a lockbolt installation tool, the pin is pulled to bring the material together at the same time the collar is pressed onto the pin to form a permanent bond with the locking grooves. The result is a tight, strong connection.
The Benefits of Lockbolts
The lockbolt design developed by Louis C. Huck is still the most common design used today. Lockbolts come in various sizes and materials for different applications, but the basic principle is the same for all applications, and provides multiple benefits:
- The lockbolt design forms a lasting joint that is stronger than a traditional screw joint or even a rivet. When a lockbolt pin is pulled during installation, the squeezing action not only reduces the diameter of the collar but also stretches the pin to generate more force over the joint.
- Lockbolts’ swaged installation makes them exceptionally resistant to loosening with vibration or material fatigue. Once the collar is swaged, the bond is permanent.
- Lockbolts exceed the performance of torqued bolts in both shear and tensile strength, so they have a longer fatigue life. The shear strength is determined by the diameter of the lockbolt and the material strength. The tensile strength is the result of the shear resistance of the collar and the number of grooves filled by the swaged collar. The higher the number of grooves in the lockbolt, the greater the bolt’s tensile strength.
- Lockbolts are easier and faster to install than nuts and bolts. Specific nose assemblies are used on the lockbolt tool to accommodate the style and diameter of the lockbolt. Swaging is performed with a lockbolt tool and takes seconds to complete. It also requires little or no operator training.
- It’s easy to visually inspect a lockbolt joint for proper installation. The Huck Bobtail® and Huck-Spin 2®, for example, feature collar tabs that show when the lockbolt is properly installed. Quick inspection can reduce costs related to warranties and rework.
- Lockbolts also come in a variety of materials, diameters, lengths, and head styles, so they can be used for almost any type of application. Lockbolts can be made of steel, hardened alloy steel, aluminum, stainless steel and titanium. Common head styles include round, brazier, truss, and low profile “rivet” head styles, each resulting in a different surface appearance. Head size matters as well; wider heads are used with softer materials, for example, to create a larger, stronger bond footprint.
Lockbolt Installation Advantages
Using lockbolts for construction and manufacturing applications offers a number of advantages when it comes to installation.
Lockbolt tools are simple to operate, whether powered by hydraulic, pneumatic, or electric methods. To form a permanent bond, simply position the lockbolt itself, fit the collar over the pin, apply the lockbolt tool, and activate the trigger. The lockbolt tool does all the work: pulling the pin to bring the joint materials together, swaging the collar, and shearing off the excess pin in one application. Installing a lockbolt takes minimal operator skill, and proper training only takes a few minutes.
When properly installed, a lockbolt will create a bond that is stronger than one offered by nuts and bolts, rivets, welding, or adhesives. It also allows considerably faster installation than tightening nuts and bolts. Unlike conventional bolts, lockbolts only require access from one side of the joint.
If you want to learn more about lockbolts, their benefits, and their applications, contact one of our fastener specialists here at Bay Supply. We are always eager to help you locate the right lockbolt or tool for your needs.