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How Concrete Fasteners Work

The process used when fastening to concrete has basically remained unchanged over the years. Although there are epoxy/chemical type anchors in use today, the majority of anchors rely on the same principles that were developed many years ago.

Fastening to concrete is unique compared to other fastening applications, such as fastening two pieces of metal together by using a screw or a bolt and nut. Concrete anchors of any type are much more difficult to use and install correctly.

The concept of fastening something to a solid base material is completely different than for almost any other type of fastening application. Concrete is the most widely used base material in the world for the last 2,000 years and probably will remain so for the next 2,000 years due to its simplicity, strength, versatility and the abundance of the ingredients used to make it.

The process with which we fasten to concrete is simple:

1. Make a hole in the concrete
2. Put something in the hole to take up the space created
3. Expand the material in the hole via a nail, screw or setting tool

We are making a hole with a certain amount of volume and then inserting more material into the hole. This increased volume of material that pushes against the interior wall of the hole will create friction. This friction is how most mechanical concrete anchors obtain their holding values.
All the mechanical type concrete anchors work on the same basic principle. Drill a specific size hole, insert the anchor, and expand the anchor larger than the hole in order to make it difficult for the anchor to be pulled out of the hole. Concrete anchors are designed to go into a hole in concrete and not come out.

Wedge Anchors

Wedge anchors are two-piece concrete anchors that are assembled into one unit. The steel rod made from carbon steel or stainless steel is threaded on one end and the opposite end starts out slightly smaller in diameter and tapers out to the full diameter of the rod. A clip is then permanently attached to this end of the rod. The wedge anchor is inserted into a hole in concrete until the threads are below the surface of the concrete. The nut and washer are placed on the threads and tighten until finger tight. Using a wrench, the nut is then turned, which pulls the anchor up to wedge the clip between the stud and the wall of the concrete. When drilling a hole in concrete for a wedge anchor, the hole size is equal to the anchor diameter size. concrete driveways sydney

Sleeve Anchors

The sleeve anchor is made up from four different parts. The stud, which is threaded and flared or cone shaped at one end, the expander sleeve, and the nut and washer. The expander sleeve is assembled over the stud with the nut and washer threaded on to the opposite side of the cone shaped end. The sleeve anchor is inserted into a hole drilled in the base material either concrete, brick or block. The nut is turned, which pulls the stud up through the expander sleeve, expanding it up against the inside wall of the base material. The hole size to be drilled into the concrete for a sleeve anchor is equal to the diameter of the anchor being used.

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