What Are Anchor Bolts?
In the world of masonry, anchor bolts are a vital part of any building or renovation project. Unavoidable when you need to attach anything to a wall made from bricks or blocks, anchor bolts have been in use for centuries and have evolved through many different stages.
As far back as Roman times, anchor bolts were being used to construct stadiums and arenas – without them it is unlikely that patrician buildings would have survived. In fact anchor bolts can be found in just about every corner of society, including residential housing and public works.
What is an Anchor Bolt Used For?
Anchor bolts are generally used to connect two or more structural parts to bricks, plaster or concrete. For example, if you need to connect a beam to a brick wall, you will firstly drill holes in the wall and beam, then insert the anchor bolt through the wooden beam, into the wall and tighten with a wrench.
How do Anchor Bolts Work?
As you tighten sleeve anchor bolts, the expansion sleeve expands in the pre-drilled hole causing a tight fit and anchoring the bolt firmly in place. Whereas with a straight-forward bolt, a nut is used to compress both elements together. Obviously, to allow this to happen you need access to both ends of the bolt, but with most masonry fixings, you simply pre-drill a hole, place the bolt in and start to tighten. This pulls the tapered cone sleeve toward to opening, causing the sleeve to expand within the hole, securing it in place.
Types of Anchor Bolts
Anchor bolts are sometimes referred to as sleeve anchors because of the design and action of securing. They are made from stainless steel or bright yellow zinc plated and can be topped with a hex bolt or countersunk, depending on your requirements.
There are four types of anchor bolts:
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Double-end Rods with Plate
These types have double-end rods with a plate washer at one end. They are used in such instances like construction of highway signs and building columns.
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L-shaped
These are embedded in concrete with the hook or L-shaped bar left protruding above the concrete.
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Headed Anchor Bolt
These bolts generally have a large hex or square bolt head and is used mostly in construction projects.
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Swedge bolts
Mostly used in major construction projects, these bolts have a thread on one end and indentations on the other. The indentations are used to grip against wet concrete, so they become solid and twist resistant when the concrete dries.
How are Anchor Bolts Installed?
- Firstly, drill a hole in the wall, the size of the drill bit to be used will be recommended by the anchor bolt manufacturer.
- Make sure the depth of the hole is larger than the length of the bolt. Remove all debris from inside the hole with a blow out pump to ensure a good fixing. Slide the sleeve bolt in.
- Push the washer onto the bolt and make sure it is flush against the top of the bolt and the wall.
- Tighten the nut on the bolt until you hear a click, this ensures the sleeve is engaged within the hole and the secure fixing of the bolt begins.
- Now you can remove the nut from the bolt and attach the other element of your fixing, before re-attaching the nut to the bolt and securing everything in place.
How to Remove Anchor Bolts
Removing a pre-installed anchor bolt can be easy if it is a fairly new installation or more difficult if the nut and bolt has become rusty. Using a variety of wrenches, twist the nut to release it. Sometimes hitting the wrench with a hammer will also jolt the nut enough to allow you to release it. If it has rusted too much, try spraying with a lubricant first to clean the joint. Lastly, use a hacksaw to cut through the bolt and nut. This will shear the anchor bolt enough for you to free the attached elements.
Anchor Bolt Sizes
Stainless steel sleeve bolts come in various sizes from 6mm in diameter to 12mm. The length also varies from 40mm to 100mm. Our zinc and yellow bolts range in size from 8 to 20mm and 40 to 150mm in length. Other sizes are available.