Applications for Lag Shields
When you need a fastener solution that can be used for a variety of base materials, including concrete blocks or bricks, lag shield anchors may represent your best option. Designed for use in combination with lag screws, lag shields have a length designation of either short or long. Typically, the long anchor shield works for softer, less dense base materials. The short lag shield works best for hard, dense base materials.
How Lag Shields work
The length of the lag screw is critical for ensuring that the shield can expand properly. To find a lag screw with sufficient length, consider the depth of embedment of the shield, the thickness of the material being fastened and the space required for any washers.
You can refer to a lag shield anchor by the size of the lag screw, or by the inside diameter of the anchor. Available in both short and long lengths, lag shields come in five different diameters:
How to Install Lag Shields
Start the installation by drilling the hole. The depth should be at least equal to the length of the lag shield you will install, but with a diameter that is larger than the designated size of the lag shield anchor. For example, a 3/4” lag shield requires a 1” hole. Use a vacuum to clear the hole of all dust and debris. Then, clean the hole with a wire brush that has the same diameter as the hole.
The length of the lag screw requires you to add the thickness of the material you will fasten to the length of the anchor and the thickness of any washers. You can embed a long lag shield, as compared to a short shield, deeper into the base than the required minimum, if you would like to achieve a higher holding value. Use the depth gauge on your hammer drill to determine the correct depth of the hole.
Next, hold open the end of the shield and insert the closed end into the hole. With a slight tap of the hammer, set the lag anchor flush to the surface of the base material. Line up the holes on the fixture (item to be fastened), with the shield and insert the correct-length screw through the fixture and into the lag shield. Tighten by hand.
With a wrench, turn the lag screw counterclockwise until it’s tight against the surface of the item being fastened. Be careful not to use too much torque on the screw, because it may cause the shield to spin in the opening and lose its holding value.
Achieving Maximum Lag Shield Anchor Strength
Proper placement of the lag shields in the base material plays an important role in the expansion forces that occur when the lag shields are transferred to the base material. If you place the lag shields too close together, the interaction between the lag shields can lead to a decrease in holding value for the adjoining anchors.
You should place lag shields a minimum of 10 anchor diameters away from one another, and at least five anchor diameters away from any unsupported edge. You should increase the anchor spacing if a possibility exists for unexpected vibratory or impact loads.