Frequently Asked Questions
Q: How many types of wedge anchors are available?
A: There are five types of wedge anchors that are categorized based on the steel in which they are made of and the coating that protects them. Zinc plated wedge anchors are not recommended for outdoor use since they have low rust resistance. Galvanized wedge anchors (both hot dipped and mechanically galvanized) can be used in unpolluted, exterior environments because they provide moderate rust resistance. There anchors can also be used in humid environments. Stainless steel wedge anchors are available in 3 different types of stainless steel including 303, 304 and 316 stainless steel. Type 303 and 304 perform equally well in certain corrosive environments. For the greatest degree of corrosion resistance, use the Type 316 stainless steel wedge anchor.
Q: Will a wedge anchor break when it reaches its maximum holding values?
A: No, the concrete gives out before the wedge anchor breaks in most cases. Holding values are ultimate holding values for the embedments shown. A safety factor of 4:1 (or 25%) is generally accepted as a safe working load. For example, if the ultimate shear load for a 1/2" diameter wedge anchor in 4000 psi concrete is 9,377lb., then the safe working load for that anchor would be 2,344lbs. Remember that this is the holding value for one anchor only.
Q: How much thread is on a partially threaded wedge anchor?
A: The partially threaded wedge anchor is threaded for about a third of its length. The diameter of the unthreaded portion is less than the nominal diameter. The foremost benefit of the partially threaded wedge anchor is that it can not be successfully installed in a hole that does not meet or exceed minimum embedment requirements.
Q: Which is the best type of wedge anchor?
A: Wedge anchors are available in 9 diameters- 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 7/8", 1" and 1-1/4" and a wide range of lengths. Wedge anchors are also manufactured with different thread lengths. Some manufacturers prefer to offer a fully threaded wedge anchor, while others produce partially threaded anchors. There are pros and cons to both types of anchors and the better choice is still heavily debated among professionals in the industry.
Q: How do I know what size anchor I need for my job?
A: Determining the size of anchor required for your application is fairly simple. Anchor diameter required is typically dependent upon the hole in the fixture itself. To determine the wedge anchor length needed simply add the thickness of the fixture to the minimum embedment for the diameter being used plus the thickness of the nut and washer (approximately equal to the anchor diameter itself). In other words: Thickness of material + minimum embedment + thickness of nut/washer = minimum anchor length
Q: What is stronger, the wedge anchor or the concrete that it is installed into?
A: Wedge anchors have excellent holding values. The holding power of any anchor depends on the quality of the concrete itself. Holding values are based on the depth of embedment- deeper embedment=better holding values. When comparing technical data for different manufacturers, it is important to determine what values are given- ultimate load ratings or working loads. Either term is acceptable but it is important during product comparisons that the equivalent values be used.
Q: How does a wedge anchor work?
A: Wedge anchors are two-piece concrete anchors that are assembled into one unit. The steel rod is threaded at one end and the opposite end starts out slightly smaller in diameter and tapers out to the full diameter of the rod. The wedge anchor is inserted into the hole in concrete until the threads are below the surface of the concrete. The nut and washer are placed on the threads and tightened until finger tight. Using a wrench, the nut is turned which pulls the anchor up to wedge the clip between the stud and wall of the concrete. When drilling a hole for a wedge anchor, the hole size is equal to anchor diameter.
Q: Why is fastening to concrete with a wedge anchor such a bigger job then fastening two pieces of metal together?
A: Fastening to concrete is a unique process. Concrete anchors are more difficult to install and use. Fastening something to a solid base material is different than almost every other type of fastening. Concrete is the most widely used base material in the world due to its simplicity, strength, versatility and abundance of the ingredients used to make it.
Q: How has fastening to concrete and using wedge anchors changed over the last 25 years?
A: The process of fastening to concrete has basically remained unchanged over the years. Although there are epoxy/chemical type anchors in use today, the majority of concrete anchors still rely on the same principles that were developed many years ago.
Q: Is it safe to use wedge anchors to hang a light fixture over a shipping table on a concrete ceiling?
A: 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 important that an engineer be consulted. Most cities have certain codes and differ from city to city. These codes should be checked before installing concrete anchors or beginning a project.
Q: Is it important to clean out the hole before I install wedge anchors?
A: Removing all dust from the hole will increase the chances of a successful installation of the wedge anchor. This dust can become airborne, therefore it is important to wear some type of mouth and nose protection so that you do not breath dust into your lungs. A wire brush, vaccum or compressed air can be used to remove this dust. Proper safety equipment is needed during this process.
Q: Why are the wedge anchors on wedge-type-anchor.com less expensive than the wedge anchors found at my local big box store?
A: Customers pay a premium price for anchors at big box stores since they are individually packaged and customers need only a couple quickly. They also pay higher prices due to convenience. Pricing at these stores is anywhere from 30-70% higher than prices found online. If larger quantities of anchors are needed, online purchasing will result in large savings and the convenience of your anchors being delivered right to your door!
Q: Why is there such a large price difference between the different materials of wedge anchors?
A: The cost of wedge anchors increase with the more rust resistance that it offers. Zinc plated wedge anchors provide the lowest level of rust resistance and are the least expensive. Hot dipped galvanized wedge anchors offer moderate rust resistance and are about twice as much as zinc plated anchors. Stainless steel wedge anchors provide excellent corrosion resistance and are the most expensive type of wedge anchor.
Q: Are stainless steel wedge anchors rust proof?
A: Stainless steel is stain-less not stain-proof. Stainless steel is a steel alloy with a minimum of 11% chromium content by mass. This amount of chromium provides a film of chromium oxide that prevents corrosion from spreading.
Q: Does the galvanizing of a wedge anchor make it stronger?
A: No, they have the same holding values as zinc plated anchors. This process is done in order to prevent galvanic corrosion. This creates a physical barrier for the exposed steel. Hot dipped galvanized anchors are favored over stainless steel because of their lower cost.
Q: How many steps are required to properly install concrete wedge anchors?
A: The wedge anchor installation process is simple and requires 5 steps:
1. Drill a hole in the base material a minimum of 1/2" deeper than the wedge anchor's embedment. Use a carbide bit and a hammer drill for best results.
2. Clean out the hole using compressed air or a wire brush.
3. Place nut on the end of the anchor before hammering into the hole in order to protect the threads during installation.
4. Hammer the anchor through the hole in the fixture and into the hole in the base material deep enough so a portion of the threads is below the surface.
5. Tighten the nut 3-4 revolutions to set the wedge anchor.
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