The Working Principle And Installation of Expansion Bolts

The Working Principle and Installation Requirements of Expansion Bolts

Expansion bolts are commonly used fixing components in both engineering and household applications. Despite being small, an expansion bolt can firmly secure objects to walls or other structures. But why is it that such a small part can hold tightly within a wall? What exactly is the state of the expansion bolt inside the wall? Let’s explore this in detail.

The Working Principle of Expansion Bolts

An expansion bolt typically consists of a bolt, expansion sleeve, and other components. The tail of the bolt is conical, with an inner diameter larger than that of the expansion sleeve. When the nut is tightened, the bolt moves outward, and the conical part moves as well. This axial movement of the bolt causes the outer surface of the expansion sleeve to generate significant pressure. Additionally, the small angle of the cone leads to friction and self-locking between the wall, the expansion sleeve, and the cone, effectively achieving the fixing function.

Components of an Expansion Bolt

1. Bolt: The bolt is the core component of the expansion bolt, providing the force mechanism. When the nut is tightened, the movement of the bolt pushes the conical part, which then expands the sleeve and creates the friction necessary for fixing.

2. Expansion Sleeve: The expansion sleeve, typically made of plastic or metal, plays a crucial role in expanding when the bolt is tightened. The expansion creates a tight bond with the surrounding wall, resulting in a secure fixation. The material and quality of the expansion sleeve affect the holding capacity and service life of the expansion bolt.

3. Spring Washer: The spring washer, a standard component on expansion bolts, is designed with a misaligned opening and elastic properties. The sharp edges of the washer dig into the nut and the flat washer to prevent the nut from loosening due to vibrations or external forces.

4. Flat Washer: The flat washer distributes the pressure from the nut evenly across the connected components. This helps prevent localized pressure, which could lead to damage or loosening.

Installation Requirements and Hole Specifications

When installing an expansion bolt, the size and depth of the hole are crucial for ensuring that the bolt functions effectively. Specifically:

1. Hole Depth Requirement: The hole depth should typically be 5mm deeper than the length of the expansion bolt to prevent debris from entering the hole, which could hinder the bolt’s full insertion.

2. Hole Diameter Requirement: The required hole diameter varies depending on the model of the expansion bolt. The standard specifications are as follows:

• M6 series: Drill hole diameter 8mm;

• M8 series: Drill hole diameter 12mm;

• M10 series: Drill hole diameter 13mm;

• M12 series: Drill hole diameter 15mm;

• M16 series: Drill hole diameter 20mm.

Expansion Bolt Installation Steps:

1. Prepare the Tools: Gather the necessary tools: a power drill and drill bits, hammer, Phillips screwdriver, and a pencil.

2. Drill the Hole: After preparing the tools, select a carbide drill bit with the same diameter as the expansion sleeve of the expansion bolt. Install the drill bit on the power drill and drill a hole into the wall. The hole depth should be approximately the same length as the bolt. Insert the expansion bolt kit into the hole, but be sure not to remove the nut. This will prevent the bolt from falling into the hole if the hole is drilled too deep, which could make it difficult to retrieve.

3. Tighten the Nut: Tighten the nut until it feels secure, around 2 to 3 turns, ensuring that the expansion bolt is snug and won’t loosen. After that, remove the nut. Align the fixture to be fixed with the bolt, and then place the outer washer or spring washer before tightening the nut.

4. Hole Size: For a 6mm expansion bolt, drill a 10mm hole; for an 8mm bolt, drill a 12mm hole, and so on. The hole diameter should match the outer diameter of the expansion sleeve. If the wall is made of soft brick, use a slightly smaller drill bit. The expansion sleeve must fit entirely into the wall. The longer the threaded portion, the deeper the sleeve goes, and the firmer the hold.

Notes:

• Surface Quality: Ensure that expansion bolts are installed into a solid material. They won’t hold well in soft or loose areas, and they may easily fall off. For example, avoid installing them in the mortar joints of brick walls or on old, damp surfaces.

• In fact, once you master the correct procedure, installing an expansion bolt is not as complicated as it may seem. It's actually quite simple! When you need to hang a picture, a frame, or a basket, just call on the expansion bolt – it’s more than strong enough to support the weight, and even a small finger wouldn’t break a sweat carrying it!

Summary

Expansion bolts are simple yet ingeniously designed fixing components widely used in construction, home improvement, and machinery installation. They create a strong frictional force within the wall or base material through the movement of the bolt and the expansion of the sleeve, securing the object effectively. Proper installation, including the correct hole diameter and depth, is essential to ensuring that the expansion bolt functions optimally and provides stability. Understanding the working principle and installation requirements of expansion bolts helps achieve better results and higher safety in practical applications.