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What Is An Expansion Bolt? The term ‘expansion bolt’ refers to an assembly that consists of three fastening components: an expanding sleeve, a threaded bolt and a properly sized nut. When employed together, the force generated from tightening the nut and bolt pushes the expanding part of the sleeve outwards, gripping the material the sheathing […]

What Is An Expansion Bolt?

The term 'expansion bolt' refers to an assembly that consists of three fastening components: an expanding sleeve, a threaded bolt and a properly sized nut. When employed together, the force generated from tightening the nut and bolt pushes the expanding part of the sleeve outwards, gripping the material the sheathing is embedded into. Due to the specific fastening system, this type of bolt is most suitable for connections between porous materials, such as brick, stone, or concrete.
expansion bolt

Types Of Expansion Bolts

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Given the fastening mechanism, it's clear that expansion bolts are typically employed in applications where the standard threading cannot be created. In spite of the numerous similarities that it shares with the nail-in anchors featuring nylon sleeves, these bolts are utilized in heavy-duty applications such as stadium seating or securing pews. There are several expansion bolt assemblies available, each serving a different role:

  • Lifetime Expansion Bolts: As their name suggests, these fasteners are designed to never be removed. They can be identified by the steel cone covering the head of the bolt.
  • Permafix Security Expansion Bolts: Commonly used to secure bars and grilles in place.
  • Anti-Tamper Expansion Bolts: Made from steel, the fasteners can be installed and removed via an anti-tamper tool.

The Lead Sleeve

In spite of the fact that all components are important, the lead sleeve is considered the heart of the expansion bolt assembly. The main reason why these bolts do such a great job at filling in the gaps in masonry, brick, or concrete, is that the sleeve is made of lead. The soft metal properties of lead makes it compliant when pressure is applied to it. Because lead is malleable, the sleeve doesn't just fill in the existing cracks, but creates more than one anchor point, providing more stability. Since the soft metal doesn't rely on a single point of attachment, it also means less chances of cracking or shattering.

Expansion Bolt Assembly Advantages

Expansion bolts are not only flexible and pliable, but they are also reliable and strong. Perhaps the most appreciated feature is that they are not dependent on the quality of the materials used. For instance, in the construction industry, you can be certain the expansion bolt will continue to do its job, regardless of the quality of the concrete or brick.
A further appreciated feature of expansion bolts is that they allow some room for error. Referring to the construction industry again, these fasteners are flexible enough to ensure a safe installation, despite the fact that the drilled holes present minor misalignments.
Since the construction industry is one sector that relies on expansion bolts for fastening, it's only natural to ask yourself whether the bolts can withstand the elements. The corrosion resistance is ensured by the steel alloys along with the zinc and cadmium plating. They are a great choice for construction as well as applications where the bolts face exposure to water.

About the Author

Larry Melone
By Larry Melone
President

Started my career in the fastener world in 1969 at, Parker Kalon Corp. a NJ based screw manufacturer located in Clifton, NJ working in inventory control, scheduling secondary production and concluding there in purchasing. In 1971 I accepted a sales position at Star Stainless Screw Co., Totowa, NJ working in inside sales and later as an outside salesman, having a successful career at Star I had the desire with a friend to start our own fastener distribution company in 1980 named: Divspec, Kenilworth, NJ. This was a successful adventure but ended in 1985 with me starting Melfast in August 1985 and have stayed competitive and successful to date. Melfast serves the OEM market with approximately 400 accounts nationally.

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