For many families, dining outdoors is the best part of warm weather. Cooking food on the grill, inviting friends and family to join, and sitting in the sunshine (or underneath the stars) makes wonderful memories.
And while dining outside, and sharing stories around the table, the table itself can enhance the experience. Pouring a concrete slab in the yard and installing a beautiful wooden picnic table creates an even more enjoyable environment for outdoor dining. Installing a picnic table in this way is a great project for families to DIY together. To install a picnic table in concrete and similar applications, strike anchors are frequently used.
Strike anchors are fasteners used for light duty fastening in concrete. They can’t be used in other masonry materials. These anchors include a body made of carbon steel and a drive pin made of carbon steel that is hardened.
The strike anchor is set in the concrete by hammering the pin down the middle of the anchor.
How to install a strike anchor
1. Prepare materials and tools
A hole will need to be drilled in the concrete to install the anchor. This should be done using a hammer drill and carbide tipped bit.
The hammer drill must be set in the hammer and rotation mode. The hammering motion breaks up the concrete while the rotation of the bit removes the dust from the hole.
The use of a rotation-only drill will not produce the required hole tolerance needed to install an anchor. Don’t use these drills for this project.
2. Plan the hole
The diameter of the hole that you’ll need to drill in the concrete is the same as the diameter of the anchor. For example, a 3/8” strike anchor requires a 3/8” hole.
Use a carbide tipped drill bit that meets ANSI standards. A bit that meets ANSI standards will help ensure that the hole tolerance will meet the tolerance required for the proper installation of the anchor.
Determine what length anchor you need. To find this out, add the thickness of the material being fastened to the minimum embedment depth, and add space for the nut and washer.
The length of the anchor is measured as an overall length from one end to the other, including the threads.
3. Drill the hole
To ensure the hole you create the concrete is the proper depth, use the depth gauge provided with the hammer or tape the bit at the required embedment depth.
To set the depth gauge, pull it out to the desired position and then lock in place. - To tape the bit, simply wrap a piece of tape around the bit at the desired depth. - It is very important that the tape or the depth gauge is set when the bit is in the retracted position, in order to ensure proper hole depth.
Drill the hole at least 1/2 inch deeper than the anchor will penetrate the base material. The extra 1/2-inch allows space for any dust created during the installation to fall out of the way.
For each diameter of strike anchor, there is a minimum and maximum embedment depth needed to achieve proper holding strength.
Embedment Depth Chart
4. Clean the hole
Before inserting the anchor into the hole, clean the hole of all dust and debris created during the drilling process.
Clean the hole by using a wire brush that is the same diameter as the hole. Use an up and down movement along with a turning motion with the brush. Then vacuum the hole. This process may need to be repeated.
Compressed air can be used to clean out the hole, but it creates a lot of airborne dust and may not be suitable for some environments.
5. Install the anchor
The expansion pin comes assembled in the anchor body. The nuts and washers are packaged separately from the strike anchor, and they must be placed on the anchor before installation.
Place the washer over the threaded end of the anchor. Place the nut on the threaded end then turn the nut clockwise onto the threads of the anchor body until the top of the nut is flush with the top of the anchor body. This will protect the threads of the anchor during the installation process.
The anchor can be installed through a fixture or directly into the concrete with the fixture placed over it.
DIRECTLY INTO CONCRETE
Insert the slotted end of the anchor directly into the predrilled hole until the washer and nut is tight against the surface of the concrete.
With a hammer, hit the expansion pin with sharp blows until the head of the pin is tight against the anchor body. The anchor is now set and the nut and washer can be removed.
The fixture can be placed over the anchor, washer, and nut and then snugged up.
It is very important that the nut is not over torqued, as this may cause the anchor to spin in the hole and cause a decrease in the holding values.
Insert the slotted end of the anchor through the hole in the fixture and into the hole in the concrete.
The hole in the fixture must be slightly larger than the designated diameter of the sleeve anchor. This is necessary because the designated diameter of the anchor is larger than a true measurement.
Below is a chart showing the minimum size hole that must be in the fixture for the anchor to fit through. Once the nut and washer are snug against the surface of the fixture, then the nut can be turned with a wrench until tight. It is very important not to over torque the nut as this may cause the anchor to spin in the hole and result in decreased holding values.