Drilling holes in concrete must be done using a hammer drill and a carbide bit. The concrete is broken up into small pieces by the hammering motion of the drill and the rotation pulls the material out of the hole. Small pieces of concrete can fly out of the hole and may enter the eye. It is always important to wear safety goggles when drilling holes in concrete. Airborne concrete dust may be also be created depending on the dryness of the concrete- mouth and dust protection should also be considered when holes are being drilled in the concrete.
Hammer drills are used for drilling holes into concrete and are manufactured by many large tool manufacturers around the world. It is very important to follow all of the manufacturer's safety measures for the hammer drill being used. Most of these hammer drills come with a grounded electrical cord with instructions on what type and lengths of extension cords should be used. Many times when drilling holes, the bit may get bound up in the hole. The larger the hole and hammer drill, the more critical this is since these drills are very powerful with lots of torque. Most brands of hammer drills have clutches built into them that allow for the drill to clutch out if the drill bit gets bound up in the hole. This is a very important safety feature- make sure that the hammer drill has a clutch. Most drills are sold with a detachable hand grip that fits on the drill and swivels 360°. Use the handgrip because it will allow for two-handed operation of the hammer drill. This is critical in the safe use of this tool.
The installation of concrete anchors requires numerous tools other than hammer drills. Once the hole is drilled, there is concrete dust that must be removed from the hole and the area around the hole. This dust can become airborne, therefore it is important to wear some type of mouth and nose protection so that you do not breath the dust into your lungs. A wire brush, vacuum or compressed air can be used for this procedure. The wire brush and compressed air can make a large concrete dust cloud. With the proper safety protection and equipment, you will be protected from these hazards.
Depending on the particular type of concrete fastener being used, there are a number of different tools that are required to set the anchor in place. Most concrete fasteners require the use of a hammer. It is important to make sure that the hammer is heavy enough for the job. Large wedge anchors require a large hammer to anchor into the hole in the concrete. Some anchors, such as the drop in and machine screw anchor, require the use of a setting tool. This setting tool is a piece of steel that is inserted into the anchor and then struck by a hammer setting the anchor in the concrete. Anytime a hammer is used, eye protection should always be utilized. Concrete anchors either have a nut that needs to be turned or a bolt that requires the use of a wrench. The manufacturer safety recommendations should be also be followed. The correct size wrench is also important to consider.
The friction created between the anchors and the walls of the hole in the concrete create the holding values of the concrete. The holding values of concrete fasteners are broken up into 2 categories- pullout/tension and shear. The shear values are directly related to the diameter of the anchor or bolt being used and the depth of embedment into the concrete as well as the strength of the concrete the anchor is in. The pullout or tension values of an anchor derive its value from the depth of embedment of the anchor, the strength of the concrete and the diameter of the anchor being used. Each anchor has a minimum embedment depth that must be achieved for the anchor to have much or any holding value. Each type of concrete anchor has been tested for holding values at different embedment depths and strengths of concrete. Each manufacturer has its own tables outlining these values. Each should be read carefully in ensuring the proper choice of anchor for the particular application. Some of the tables refer to "Ultimate Loads" and others show "Safe Working Loads". The difference for comparing two tables from two manufacturers is that safe working loads are 25% of the ultimate loads. When setting an anchor, it is important not to over torque the anchor because it may spin in the hole and not achieve the holding powers required. Below are links to holding value tables for wedge anchors, sleeve anchors, Tapcon® concrete screws and drop-in anchors.
One of the most critical places to use a concrete anchor is in overhead applications. If the anchor or concrete should fail, the consequences could be deadly. If the application calls for overhead installation, it is imperative that an engineer is consulted. Most cities have certain codes and these can differ from city to city. These codes should be checked before installing concrete anchors or beginning a project
As 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.