The first question which comes to mind when someone mentions expansion bolts is “What is an expansion bolt?”. The next one is along the lines of “What is an expansion bolt for and how does it work?”. This article should answer some of these questions for you.
An expansion bolt is made up of a bolt, nut and a sleeve. The sleeve expands when the bolt is tightened. They are similar to nail-in anchors but are capable of handling much more heavy duty usage such as podiums and stadium seating. There are a few different types of expansion bolts available. A definition from a mechanical engineering point of view is as follows: an expansion bolt is a bolt and nut configuration that expands when tightened into a hole.
The first is the bolt, lead sleeve and tapered nut combination. The nut is inside a lead sleeve and the whole thing is put into a hole already drilled into the material that needs to be fastened. The bolt is then fastened and the nut is pulled up towards the bolt head and this makes the lead sleeve expand and tighten in the hole.
Then there is the bolt, lead sleeve, metal cone and nut combination. The cone and sleeve lie on the bolt assembly. As the bolt is tightened, it forces the metal cone into the sleeve which again causes the sleeve to expand and fix the equipment in place.
The common factor is the lead sleeve. It is this that actually facilitates the expansion and allows the bolt to stay in place. The sleeve also protects the bolts and the material from cracking from too much pressure. It also decreases the chances of the bolt getting pulled out or stripped.
Expansion bolts are rated on the tonnage they can handle. They should be chosen according to what use they will be put to and what kind of stress they will be under as well as what kind of corrosion can be expected.
One of the more common uses that can be seen and understood by just about any one, is in the protection on climbing routes in cliffs and mountains. The expansion bolts are put in places that are likely to have accidents happen to provide anchors for the climbers to attach to. zip ties
So, expansion bolts are not that complicated. They basically are a bolt in a sleeve that expands when the bolt is tightened. The expansion makes the bolt stay more securely in the hole. The sleeve protects the bolt and also the material it is being inserted into. Expansion bolts can be used in the construction of podiums, permanent scaffolding, seating in stadiums and security on rock climbing routes.
They are fairly easy to use, all you need is the correct drill bit, at most only a little larger than the bolt head itself and the bolt. Drill a hole into the material, insert the bolt and tighten it. Be careful not to over tighten it as that may cause the head of the bolt to get stripped rendering the bolt very difficult to remove, if not impossible.