Blind bolts have been used for manufacturing and repair for decades. Because they come in all sizes and designs, it can be a challenge selecting the right fastener for the job. Choosing the right blind bolt is a matter of assessing the parameters of the application and choosing the right blind bolt to deliver maximum strength. You want to ensure that the blind bolt is easy to install, yet will be strong enough to create a lasting join.
A blind bolt is a fastener designed to deliver more strength and longer performance than a rivet or weld. They are called “blind” because they are installed from only one side of the material to be joined—very useful for repair and manufacturing applications. They also were designed for installation in tight spaces where conventional rivets or hexagonal nuts would be hard to use.
A typical blind bolt is inserted through a predrilled hole. When tightened, it expands on the blind side to form a strong join. The blind bolt itself consists of a steel pin, a collar, and a sleeve. When it’s tightened, the collar creates pressure that collapses the expander on the blind side, and the sleeve collapses to create a seal on the visible side. They are easy and fast to install, easy to inspect, and create a strong and lasting connection. That’s why they are popular for applications such as construction to hold steel girders together.
Choosing the right blind bolt is a matter of matching the size and strength of the bolt to the job.
Choosing the Right Blind Bolt
When you are determining which blind bolt is best for the job, there are various factors to consider, such as:
- Strength – The strength of the blind bolt relates to the length of the fastener. The grip is the total thickness of the materials being joined by the fastener. The grip length of the bolt should be the distance from the underhead surface to the first thread of the pin shaft and should be a fraction less than the actual grip. Grip gauges are inserted into the predrilled hole to determine the right bolt size, but gauges are unique to each manufacturer.
- Tensile strength – Depending on the application, you want to be sure that the blind bolt you choose has sufficient tensile strength and shear resistance for the task. If you choose a bolt that is too narrow or made of the wrong material, it won’t last—even though the initial bond may be extremely strong.
- Size – Blind bolts come in various thicknesses and lengths. You want to choose a bolt that is large enough to do the job, delivering maximum strength.
- Vibration resistance – One of the great strengths of the blind bolt is that it won’t loosen with continual vibration. That’s why they are so popular for heavy-duty applications, such as shipbuilding, bridge construction, mining equipment, manufacturing equipment, or any situation in which continuous vibration is a factor. Be sure to use the correct locking bolts that will resist vibration.
- Corrosion – Blind bolts are made of various materials. For example, many blind fasteners have an alloy steel stem, black oxide sleeve, and zinc-plated carbon steel collar. Other materials are available as well, such as titanium. It pays to choose the right materials for the application. In shipbuilding, for example, or other applications where the join is exposed to a corrosive substance such as sea water, choose materials that are less likely to corrode.
The Best Blind Bolts
Bay Supply carries two lines of blind bolts.
The Avdel Avbolt is designed for heavy-duty applications such as construction, railway car manufacturing, containers, mining, and even bridge assembly. Avbolts offer high tensile and shear strength and are easier to install in tight spaces. They also have a locking feature that makes them more resistant to vibration, and they are extremely tamper-resistant. Additionally, they have simple tooling, so they don’t require a lot of training to install.
The Huck BOM® (blind, oversized, mechanical) blind bolt is extremely vibration-resistant and has a unique push-and-pull installation design. Anyone can learn to install these fasteners in 10 minutes. The BOM can replace welding and is easy to inspect; if the pin position is correct on the visual side, then it has formed correctly in the blind side. The BOM is extremely accurate and tough and is used for everything from military vehicles to amusement park rides.
No matter what the application, Bay Supply has a wide range of blind bolts in stock for every use. Contact one of our fastener experts to discuss your blind bolt needs—with our decades of industry expertise, we can recommend the right bolt for your job.