Mechanical Anchors: How to Choose the Right Anchor

Different types of anchors for different uses

As mentioned above, the wide offer of anchors on the market requires good knowledge of them in order to choose the right ones suitable for one's work. In general, three main elements must be kept in mind:

• The material in which to insert the anchor (whether solid or hollow);
• The maximum weight that the anchor can support;
• The diameter of the hole in which the anchor is to be inserted.

The large family of anchors can be divided into two specific macro areas:

1. Anchors for solid materials, which include:
   - Expansion anchor bolts in metal
   - Strike anchors
   - Bolt anchors
   
   
2. Anchors for hollow walls, which include:
   - Deformation anchors
   - Self-drilling anchors
   - Toggle anchors

The most common types of anchors, easy to use and fasten, are the following:

• Universal anchor with rim
• Standard nylon anchor
• Extended universal anchor with galvanized screw
• Brass anchor
• Mechanical anchor

The weight to be supported is definitely a fundamental factor in choosing the right anchor.
The criteria related to weight are indeed the length (which is established based on the thickness of the support) and the diameter. In detail, the choice could be based on the following guidelines:

• Weight < 20 kg = diameter between 4-5 millimeters;
• Weight between 20-50 kg = diameter between 6-8 millimeters;
• Weight > 50 kg = diameter greater than 10 millimeters (these are the so-called anchors for heavy loads, hence, mechanical anchors).

Note: The indications just mentioned can be taken as general guidelines.
Indeed, such values can vary in reference to various basic factors such as, for example, the product, the supplier, and the final use.

Mechanical anchors for heavy loads

When we talk about mechanical anchors for heavy loads, we refer to mechanical fixings, i.e., fixing systems that transmit to the support the stresses resulting from the application of the load. What does this mean? Such elements work by the effect of the expansion that the anchor itself transfers by friction to the support material.

The effect of the expansion can occur in different ways:

• Tightening the nut with a torque wrench
• By screwing the screw inside the expansion body, a geometric coupling of shape with the walls of the hole made in the support material occurs (the hole must be of the right size).
• By hammering with a specific tool.

A mechanical anchor for heavy loads finds wide use in various sectors and processes. Below we report some examples of application of anchors for heavy fixings:

• Structural fixings
• Fixings in seismic zones or with a non-negligible seismic risk
• Fixings for fire escape stairs
• Fixings of parapets, railings, and balustrades
• Fixings of wooden beams
• Wood fixings on concrete
• Fixing of canopies
• Fixing of shelves or brackets
• Fixing of gates

A mechanical anchor is therefore an element that allows fastening by friction or interlocking.

As specified in the previous paragraph, the weight to be supported is linked to the diameter and length, criteria to be used to make the right choice.

Chemical or Mechanical Anchor?

When the wall's holding capacity does not allow for the fixing of the classic mechanical anchor, a valid alternative is the chemical anchor.
This type of element allows for fixing to the wall through threaded rods that are fixed with special rigid glues.

Unlike mechanical anchors where fixing occurs by friction or interlocking, a mechanical anchorage involves the use of an adhesive inserted into the hole. This adhesive, which hardens in a very short time, practically locks the screw in place.
The use of the chemical anchor is particularly recommended in cases where one does not want to compromise the integrity of the structure, thus avoiding cracks or splits. Indeed, by injecting the glue into the hole, this anchorage allows for the fixing of heavy loads even on more fragile walls. Among the advantages of such an anchor are its long duration, resistance to heat, and chemical substances.

If you're wondering which anchor, chemical or mechanical, is the best, the answer lies in the type of job to be performed. For example, if the characteristics of the support are critical or the object to be fixed is subject to a load that varies over time, then the chemical anchorage is safer because it glues to the wall and becomes one with the bricks.
Conversely, if the fixing system does not require special attention, the plastic or steel anchor ensures the hold.

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