What Is A Blind Bolt Used For?

Blind Bolt NZ | 6th August 2020


Blind Bolts

If you need a structural fastener which combines flexibility and versatility with being stronger than rivets or welds, then take it from us, you need a blind bolt. A structural fastener is generally used to fasten steel to steel connections such as girders and plates in bridges and buildings. This blog will explain what a blind bolt is and how you can use it.

What is a Blind bolt?

The clue is in the name – a blind bolt enables you to create a fastening through pre-drilled holes when you only have access to one side of that fastening and the other is hidden.

There are three parts to a blind bolt – the steel pin, the sleeve and the collar. When you tighten a blind bolt two things happen; the pressure from the collar causes the expander to collapse on the hidden side of the bolt, while on the visible side the sleeve collapses to create a seal. The connection created in this way is strong and durable, and the blind bolts themselves are easy to install and inspect. This makes them the obvious choice for sectors like construction, where they hold steel girders together.

The Uses of a Blind Bolt

Blind bolts were originally developed in order to create strong connections in locations where access restrictions prevented the use of rivets or hex bolts. For decades they’ve been the solution of choice in sectors such as manufacturing, construction and repair work when access is restricted.

How to Choose the Right Blind Bolt

Choosing the right blind bolt is all about matching the size and strength of that bolt to the job in hand. Getting that just right means thinking carefully about several factors before deciding which blind bolt you need.

Strength and Tensile Strength

The grip refers to the total thickness of the materials being joined together by a blind bolt, while the strength of that blind bolt is the strength of the fastener. Getting the grip length right is vital; it should be the exact distance from the underhead surface to the first thread of the pin shaft, and this should be fractionally less than the actual grip itself.

The tensile strength needed depends upon the individual application. You need to be certain that the blind bolt you choose has a tensile strength and shear resistance to meet the demands placed on it. For bolts across the board, the shear resistance is a measure of the maximum load that can be supported when applied to the axis of the bolt at a right angle, before the bolt fractures

Getting these two measurements right is vital – if the bolt you use is constructed of the wrong material or is too narrow then even an extremely strong initial bond is simply not going to last. Put simply, if the bolt in question doesn’t match the design specifications it will wear and become damaged much sooner than a bolt that does, and that’s something which will hit your bottom line in the long run.

Vibration Resistance

Another key plus point of blind bolts is that continual vibration won’t cause them to work loose. This simple fact makes them an extremely popular choice for high impact applications such as constructing bridges, making manufacturing and mining equipment and shipbuilding. No matter what the application, if continuous vibration is a factor, blind bolts are the solution.


We manufacture blind bolts from a wide range of materials, including titanium. Many individual fasteners have an alloy steel stem, black oxide sleeves and zinc-plated carbon steel collars, and a golden rule is that choosing the right material for your application is vital. In shipbuilding, for example, the joints are likely to be exposed to the corrosive properties of sea water, so the ideal materials are likely to be those such as A4 stainless steel, which have a high resistance to corrosion and so will maintain their strength for longer.

Bolted Shut

Blind bolts are so versatile that we’re constantly being surprised by the new and exciting ways that our clients find to utilise them. As well as saving you time and money this kind of innovation has spurred us on to increase the range of sizes we offer to meet customer demand.

Interested in finding out more about our blind bolts? Then feel free to get in touch and speak to a member of the Blind Bolt team today on 0800 42 52 62 or send us an email on enquiries@blindbolt.co.nz. We look forward to hearing from you.


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