Double Expansion Masonry Anchors
Concrete Anchors for Masonry Screws or Bolts
Double expansion shield anchors are medium-duty anchors that distribute themselves to pre-drilled hole walls evenly. This is done by expanding from both sides of the anchor for full contact and a secure hold in the base material. This makes double expansion shield the best choice for preventing cracking in brick and block and is the best choice for anchoring to brick in general. The even distribution of the anchor's expansion also makes it well suited to base materials that are suspect in quality, either because they are sandy or soft. They have the best chance to get sufficient holding power in such materials.
This anchor consists of four parts -- a two-piece tubular shield, a hollow, wedge-shaped cone, and a wedge-shaped nut -- brought together into a single anchor unit. A pair of spring bands connect the shields. At one end is the nut, and at the other, the cone, each designed to not turn during expansion.
They are used in soft masonry with machine screws or machine bolts exposed to vibration or side pressure. Inserting the machine screw into the anchor is what causes the anchor to expand and set. As the anchor sets, the opposite ends pull towards each other, causing the anchor body's elongation. It doesn't fracture and allows for fastening of any length. It can also be used in harder materials, including stone, brick, concrete, or block.
How to Install Double Expansion Masonry Anchors in Brick
How does a double expansion anchor work?
Double expansion anchors have expansion shields and wedges on each end of the anchor. As a screw is inserted and fastened into the anchor, the anchor's upper and lower sections begin to compress together. The wedges at each end get closer to each other, expanding the shield portions evenly outward. This creates a secure connection to the walls of the hole the anchor was inserted into, anchoring it into place.
What is the difference between wedge and expansion anchors?
Wedge anchors use an expansion mechanism around one end involving a wedge and a small expansion shield. As the wedge anchor is pulled up when tightening the nut, the wedge is pulled up into the expansion shield, which causes the shield to expand and lodge itself into the concrete it's installed into. Expansion anchors, such as the double expansion anchor, work similarly, using wedges or wedge-like elements to push the expansion shield outwards into the base material. Technically speaking, a wedge anchor is a type of expansion anchor, though not every expansion anchor is a wedge anchor.
What are expansion anchors?
Expansion anchors are anchors designed for use in masonry materials that provide holding power through an expansion mechanism. This mechanism lodges the anchor into the walls of the hole they are installed in, securing them in place. This mechanism can vary in appearance and exact method of expansion, but the principle remains the same. The vast majority of masonry anchors work in this way, including wedge anchors, double expansion anchors, sleeve anchors, lag shields, hammer-set or drive pin anchors, and drop-in anchors.
How do you install expansion anchors?
To install a double expansion shield anchor, drill a hole large enough to drop the anchor in and then install the screw into the anchor. As you fasten the screw, it will pull the bottom towards the middle and force the top down to the middle as well. Refer to the chart below for hole diameters and other specifications regarding double expansion anchors to help you choose the correct anchor for your application.
|Thread Size:||Recommended Hole Diameter:||Minimum Diameter of Shield Body:||Minimum Length of Shield Body:|| Proof Test Load |
(Ultimate Tensile Strength in 3000 psi. strength concrete)
Note: Double Expansion Anchors are sized based on the thread size they are compatible with.