Some joints you can only reach from one side like a sealed wing box, a closed composite panel, a fuel tank skin. You cannot get a wrench behind it, so a standard nut and bolt cannot be applied. That is the problem blind fasteners solve, and it is where Composilok fasteners earn their place.
Before you order, though, you should know what you are buying and what to ask the supplier. Let’s break it down.
What Composilok Fasteners Actually Do
Composilok fasteners are blind bolts. You install and inspect them from one side of the structure, which matters when the back is sealed or buried.
The design centres on one idea. As the bolt sets, it forms a large footprint on the blind side, and that spreads the clamping load over a wider area. The large footprint distributes the joint preload, which virtually removes the chance of delaminating a composite panel. For composite work, this is the whole point. A small contact area can crush the layers, and these bolts exist to avoid that.
Monogram Aerospace makes the Composi-Lok family, and it suits composite laminates as well as metal structures. A typical unit has a threaded stud with a tapered head and a mating nut.
Why the Material Question Matters
Here is a detail people skip. The metal in the fastener has to get along with whatever surrounds it.
Carbon fibre and aluminium do not mix well. An aluminium fastener in a carbon laminate triggers galvanic corrosion that eats the aluminium and degrades the composite, so titanium and passivated stainless steel are the usual picks for carbon assemblies.
So ask your aerospace fasteners supplier which alloy and finish they are quoting, and why. A good one answers without hesitating.
Standards Your Supplier Should Meet
A blind bolt that fails in service is not a small thing. The paperwork behind it matters as much as the part itself.
Ask whether the aerospace fasteners supplier holds AS9100. It is the quality management system standard for aviation, space, and defence, developed by the International Aerospace Quality Group and published by SAE International in the Americas. If the parts go through plating or heat treating, those steps should carry Nadcap accreditation. The Performance Review Institute runs Nadcap, and it audits the process rather than the whole company.
Questions to Ask Before You Order
You do not need to be a stress engineer to vet a supplier. Plain questions tell you plenty:
- Which Composilok variant fits your grip range and hole size?
- What alloy and finish do you have, and does it suit your structure?
- Can they show AS9100 certification and material certs?
- What is the real lead time, not the hopeful one?
- Will they supply installation tooling guidance, or just the parts?
That last one trips people up. The right tool sets the clamp force, and the wrong driver can wreck both the bolt and the panel.
Picking Composilok fasteners is not only about the bolt. It is about who supplies it and whether they can prove the part is what they claim. Ask early, ask plainly, and let the answers tell you who to trust. The cost of guessing here shows up later, usually at the worst time.
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