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Essential Definition: What is a Lockbolt?



What is a Lockbolt?

Lockbolts are just what they sound like—bolts that lock in place when installed so they won’t loosen over time, even with extreme stress and vibration. Lockbolts are used in a variety of applications in place of a rivet or conventional bolt because of their superior strength and lasting performance.

A lockbolt consists of two pieces, a pin and a collar. They can be installed in place of nuts and bolts or rivets, but with greater strength than a rivet or bolt and without the need for additional pieces such as cotter pins or lock washers to secure them in place. A lockbolt can even be installed from one side of a workpiece; it is set from the collar side and the collar is pulled and swaged onto the lockbolt during installation, so you don’t need to apply torque from both sides as you would with a nut and bolt. This makes for fast and easy installation.

Let’s Talk Pintails

Lockbolts also come in two basic designs: those with separating pintails and those without separating pintails.

Lockbolts with separating pintails are designed with a breakpoint in the pin so the tail separates when the installation is complete. The spent pintail is either ejected to the floor or collected in a container, if the installation tool is designed with a containment system. The pintails have a narrower diameter to define the breakpoint, and some lockbolts have multiple breakpoints so they can accommodate joints of different thicknesses. Unlike a nut for a traditional bolt, the collar is set and swaged and pulled onto the pin so it won’t turn during installation. Once the lockbolt is set, the breakpoint removes the excess pin.

Lockbolts without separating pintails do not have a breakpoint in the pin, so the pin remains after installation. Depending on the application, lockbolts without pintails have two advantages: First, there is no spent pintail that needs to be collected after installation. Second, there is no loud bang when the pintail separates, which reduces noise and operator fatigue.

Lockbolts Are Extremely Tough

Lockbolts are useful for manufacturing and construction applications in which there is heavy vibration because they will not shake loose. They are tougher than rivets or screw joints.

The swaged locking collar is what gives lockbolts their lasting strength and performance. Even the most closely machined nuts and bolts have gaps in the bolt thread. The swaged collar forms a tight and permanent bond with the circular grooves of the bolt itself.

One reason lockbolts are preferred over other types of threaded fasteners is they cut time, labor, and costs when it comes to installation. Using a lockbolt installation tool is extremely simple. The tool applies pressure to swage the collar, drawing the pin in as part of the installation for a tight joint. Once the collar is set, the tool can remove the excess pin (for lockbolts without pintails) and installation is complete. It’s so simple that no special training is required, and lockbolt installation is relatively foolproof and easy to inspect.

Bay Supply Carries the Leading Lockbolts

Bay Supply carries lockbolts from two of the best-known manufacturers: Huck® lockbolts, which are made by Arconic Fastening Systems; and Avdel® lockbolts, which are made by STANLEY® Engineered Fastening.

Huck lockbolts are high-performance, permanent, mechanically locking fasteners that can be installed quickly and are tamperproof. There are six Huck lockbolts available:

  • The Bobtail® has a unique design with no pintail. It also has shallower threads to spread out the service load and increase load strength.
  • The Magna-Grip® offers a wide grip range so you can use one lockbolt for various applications. It also has a flush pin break for a cleaner finish.
  • The C50L® is an 8.8 grade large diameter lockbolt manufactured to British Standard B7805.
  • The C6L® is a 5.8 grade small diameter lockbolt made to British Standard B7805 with a wide flange collar. It is ideal for use with non-metallic materials.
  • The C120L® is an 8.8 grade small diameter lockbolt made of steel. It is; a high-tensile strength version of the C6L.
  • The Hucktainer® is a unique lockbolt with a wide head and collar for use with composite board. It will not crush the material. Once installed, it creates a moisture-proof seal.

Similarly, Avdel offers five lockbolts, in addition to the Avbolt® blind bolt, for different fastener applications:

  • The Avdelok® is a high-strength lockbolt that offers high shear strength, is vibration-resistant, and is available in various materials for heavy-duty applications.
  • The Avdelok XT® family of lockbolts are large diameter two-piece fasteners for especially heavy-duty applications such as construction, mining, and building bridges and railways.
  • The Maxlok® is a multi-grip lockbolt with high strength and vibration resistance, suitable for multiple applications so you only have to stock one bolt.
  • The NeoBolt® is a pintail lockbolt with a non-breaking stem. It is available in various sizes for lasting, vibration-resistant performance.
  • The Avtainer® has a large flange collar and wider head for attaching composite materials to metal for a watertight joint.

Lockbolts are available for virtually any fastener application. If you need help choosing the right lockbolt for the job, Bay Supply has a wide range of lockbolts, and our fastener experts will be happy to advise you as to the right lockbolt for your task.

Infographic: Guide to Huck Bolts