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Wedge Anchor : Determining Size and Material to Use

Wedge anchors are designed to fix into a concrete substrate permanently. Wedge anchors are to be installed into solid concrete only and should not be used in other base materials such as brick, AAC and hollow concrete block. A very simple mechanism allows excellent consistent holding values in concrete to be achieved. Once inserted into the hole in the concrete, the nut is turned clockwise. This action pulls the anchor body up, which slides the expansion clip down the cone-shaped working end of the wedge anchor. The clip is then expanded and wedged between the anchor body and the concrete.

Parts of a Wedge Anchor:  

• Anchor Body

  – is made from galvanized carbon steel or stainless steel; it is threaded on one end for a portion of its length while the diameter is necked down and cone shaped tapering up to the nominal diameter at its other end.

• Expansion Clip

  – is permanently attached to the anchor body around the neck down area of the anchor body, made with carbon steel and zinc plated or stainless steel.

• Nut

  – is a standard national coarse hex nut; made with carbon steel and zinc plated or stainless steel.

• Washer

  – is a standard flat round washer; made with carbon steel and zinc plated or stainless steel.

Determining Size and Material of Wedge Anchor to Use:

Diameter

– the diameter of wedge anchor to use is determined by a number of factors, such as load values requirements, diameter of hole in fixture or specified by an engineer. The heavier the object being fastened, the larger the diameter of the wedge anchor must be used. The base plate or bracket being fastened comes with a pre-drilled hole and these holes may determine the diameter of wedge anchor to be used, unless the holes are enlarged to allow a larger diameter of wedge anchor to be used. Required design applications and diameter of wedge anchor have been specified by an engineer, then the anchor diameter specified should always be used.

Length

– the length of the wedge anchor used for any particular applications is determined by the thickness of the material being fastened, the embedment depth the wedge anchor will be placed at, thickness of concrete or specified by an engineer. The overall wedge anchor length must be equal to the thickness of the material being fastened plus the embedment depth, plus space for the nut and washer. It is important to ensure that the wedge anchor length is long enough to penetrate all the way through the base plate to the concrete for secured anchoring. 

Material

– the environmental conditions where wedge anchor is fastened can have an effect. Corrosion wears metal down due to the material’s interaction with chemicals in the surrounding environment. Anchor materials and coatings are designed to protect against certain conditions. It’s important to use the appropriate wedge anchor material based on the environment in which it will be installed to prevent unwanted systemic failures. Typically to combat corrosion, the wedge anchor will need a protective coating applied such as chrome or zinc. For the highly corrosive environments, the material of the wedge anchor should beStainless Steel. 

Drilling the Holes:

To install a wedge anchor in concrete, a hole must be drilled into the concrete. The hole must be drilled using a carbide bit in a hammer drill in the hammer and rotation mode to ensure proper hole size and consistency. The tolerance between the hole size and wedge anchor size is critical for the wedge anchor to achieve its holding values.

• Hole diameter for wedge anchors equals the wedge anchor diameter being installed; a M12 wedge anchor requires a 12mm diameter hole.
• Carbide tipped bit must be in good shape to ensure proper tolerance between the hole diameter and wedge anchor.
• The hole must be cleaned out to ensure that the wedge anchor will be properly installed.
• Each diameter of wedge anchor has a minimum drilling depth that the anchor must be installed at for the anchor to achieve minimum holding values. Make sure that the hole is drilled according to the product installation guide. 

 Inserting Wedge Anchor:

• Directly into Concrete – Once the hole in the concrete has been drilled then the wedge anchor can be inserted into the hole. 

• Through a Fixture Hole – Once the hole in the concrete has been drilled, the wedge anchor can be inserted through the fixture hole and into the hole in the concrete. The hole in the fixture must be slightly larger than the nominal diameter of the wedge anchor being installed.
• Then, using a wrench, turn the nut 3 to 4 turns clockwise or until the proper torque values for the diameter of wedge anchor being used are reached.