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How Wedge Anchors Work

Tuesday, May 31, 2011
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Wedge anchors are to be installed into solid concrete only and should not be used in other base materials such as brick or CMU.  Wedge anchors are designed to go into a concrete hole permanently.
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 wedges between the anchor body and the concrete. 

Parts of a Wedge Anchor: 

  • Anchor Body – is made from 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 necked down area of the anchor body.
  • Nut – is a standard national coarse hex nut; carbon steel and zinc plated or stainless steel.
  • Washer –is an SAE standard washer; carbon steel and zinc plated or stainless steel.

Drilling the Hole:
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.  Drilling a hole in concrete with a standard rotation drill may create a hole that is not suitable and may not meet the tolerance requirements of the wedge anchor.  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 3/4” wedge anchor requires a 3/4” hole.
  • Carbide tipped bit must meet ANSI standard 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.
  • Make sure that the hole is a minimum of 1/2” deeper than the wedge anchor will penetrate the concrete.  This extra space will ensure that the wedge anchor does not bottom out in the hole and allows space for any dust to fall into that is created during the installation of the wedge anchor.

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.
    • Thread a nut onto the threaded end of the wedge anchor to protect the threads when struck by the hammer. 
    • Insert the wedge anchor, expansion clip first, into the hole. 
    • Strike the nutted end of the wedge anchor with a hammer until a minimum of 5 to 6 threads are below the surface of the concrete. 
    • Using your fingers, tighten the nut snugly.
    • Then, using a wrench, turn the nut clockwise 3 to 4 turns or until the proper torque values for the diameter of wedge anchor being used are reached.
  • 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. For example, a 3/8” diameter wedge anchor requires a hole in the fixture to be a minimum of 7/16” diameter.
  • Once the fixture hole size has been determined to be large enough to accept the diameter of wedge anchor to be installed, thread a nut onto the threaded end of the wedge anchor. This will protect the threads when stuck by the hammer. 

  • Insert the wedge anchor, expansion clip first, into the hole. 

  • Strike the nutted end of the wedge anchor until a minimum of 5 to 6 threads are below the surface of the material being fastened. 

  • Use your fingers to tighten the nut snugly. Then, with a wrench, turn the nut clockwise 3 to 4 turns or until the proper torque values for the diameter of wedge anchor being used are reached.

Embedment Depth
Each diameter of wedge anchor has a minimum diameter that the anchor must be installed at for the anchor to achieve minimum holding values.  The minimum holding values for each diameter can be found at:

/wedge-anchor-technical-specifications

Determining Size of Wedge Anchor to Use:

Diameter – the diameter of wedge anchor to use is determined by a number of factors, such as holding values requirements, diameter of hole in fixture or specified by an engineer.  The heavier the object being fastened then the larger the diameter of wedge anchor must be used.  Many times the object being fastened comes with predrilled hole. 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.  Many applications have been specified by an engineer. If an engineer has specified a specific diameter of wedge anchor for a specific applications, then the 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 wedge anchor 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 that the wedge anchor is not long enough to penetrate all the way through the concrete.  If an engineer specifies a specific length of wedge anchor to use for a specific application, the length of wedge anchor specified should be the length used.

Installation:

  1. Using a carbide drill bit that meets ANSI standards, drill the hole with a hammer drill.  The diameter of the hole being drilled should equal the diameter of wedge anchor being installed.
  2. With compressed air, vacuum and wire brush, clean the hole of all dust and debris.
  3. Thread nut onto the threaded end of wedge anchor and insert into the hole clipped end first.
  4. Strike the nutted end of the wedge anchor with a hammer until 5 to 6 threads are below either the surface of the concrete or the surface of the material being fastened.
  5. Finger tighten the nut and then. with a wrench. turn the nut clockwise until snug.  The specific torque values for the diameter of wedge anchor being can be found at:

/wedge-anchor-technical-specifications

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Always use personal protective equipmentAs with any anchoring project, it is important to keep safety in mind and follow instructions carefully. Always remember to wear safety goggles, handle all tools with extra care and follow all technical specifications. This article is meant to serve only as a basic explanation of concrete fasteners. Always refer to manufacturer's instructions or consult a contracting expert during any anchoring project.

Article Written By:
Mike Pistorino, Vice-President Operations

 

 

 

 


Concrete Fasteners, Inc. has over 40 years of experience selling concrete fasteners. We can ship out one box or a whole pallet of concrete anchors. Our products are of the highest quality... "your satisfaction is guaranteed". We ship all orders the same day the order is received.

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