What Is A Double Expansion Anchor?
A double expansion anchor is a type of masonry anchor used for anchoring into materials of questionable strength or quality. In the world of masonry anchors, most rely on deforming a portion near the bottom of the anchor once inside a hole to prevent the anchor from coming loose.
Double expansion anchors differ from other masonry anchors. Instead of the bottom portion of the anchor expanding dramatically to create a strong grip, the entire anchor expands, but only slightly, in size to distribute the pressure over the entire surface area of the anchor.
When Do You Use One?
Basically, most masonry anchors are one way entry devices; they’re not meant to come out. In large slabs of concrete, most of these anchors work fine because the concrete is so strong that the anchors can place a large amount of force against it without risk of damaging the concrete. This becomes a problem with certain masonry materials.
Brick is a perfect example of a softer small masonry material. Due to its size and shape, brick can be considered delicate. Common expansion anchors placed in brick will almost certainly crack or damage the brick.
A double expansion anchor would be used when the material being installed in is of a weak material or of questionable quality. They expand evenly and distribute their holding power over the entire hole. This minimal expansion over a much wider surface area still provides a strong holding power that does not damage the brick.
Installing A Double Expansion Anchor
To install a double expansion anchor, follow the steps below:
- Using an SDS drill bit, drill a hole into the brick the same diameter as the anchor. The hole will need to be slightly longer than the anchor in-depth.
- After cleaning out and debris from the hole, insert the double expansion anchor into the hole with the threaded portion near the bottom.
- Next drill a hole through the material that will be anchored to the brick.
- Line up the holes and use a matching machine screw to catch the threads of the anchor. The initial spins can be done by hand.
- Using a screwdriver, tighten the machine screw until it tightens against the surface of the material being connected to the brick. *Note: The length of the machine screw will vary depending on what you are attaching to the brick.
One of the unique things about double expansion anchors is that they can be easily removed from an installation hole and reused. To remove one simply take out the machine screw and it will form back into its original shape. Then it can be removed from the hole.