If you've spent any time working on airframes or heavy-duty metal projects, you've almost certainly handled a cherrylock rivet. These aren't your run-of-the-mill hardware store fasteners; they are precision-engineered "blind" rivets that have been keeping planes in the sky for a long, long time. Even with all the new composite materials and advanced bonding techniques coming out these days, there is still something incredibly reliable about the way these rivets lock two pieces of metal together.
I remember the first time I saw someone install one. It looks like magic if you don't know how it works. You're looking at a hole where you can't see the other side—maybe it's a wing spar or a tight fuselage section—and suddenly, this little piece of hardware creates a permanent, structural joint that can handle massive amounts of vibration and shear force.
What Makes These Rivets Different?
Most people are familiar with "pop" rivets. You pull the mandrel, the head bunches up, and the stem snaps off. They're great for gutters or basic sheet metal work, but you wouldn't trust your life to them at 30,000 feet. The cherrylock rivet is a completely different beast. It's categorized as a "mechanically locked" fastener.
The "lock" part is the key. In a standard blind rivet, the only thing keeping the center stem (the mandrel) inside the rivet sleeve is friction. If things get shaky or if the metal starts to flex, that stem can eventually work its way out. If the stem falls out, the rivet loses a huge chunk of its shear strength. With a cherrylock, there's a tiny locking ring that physically jams the stem into the sleeve during installation. Once it's set, that stem isn't going anywhere. It stays put, filling the hole completely and providing strength that's almost comparable to a solid "bucked" rivet.
The Mechanic's Perspective on Installation
Installing a cherrylock rivet is a bit of an art form, or at least it feels like one until you get the rhythm down. You can't just grab a five-dollar hand tool from the local hardware shop and expect results. You need a dedicated pneumatic puller with the right pulling head.
When you pull the trigger, the tool grabs the serrated stem of the rivet. As it pulls, it draws the head of the stem into the rivet shank, which expands the shank to fill the hole perfectly. This "hole fill" is vital because it prevents the parts from shifting. Then, right at the end of the stroke, the tool drives that little locking ring into a groove on the stem. You'll hear a distinct "snap," and then the excess stem breaks off flush.
It's a satisfying feeling when it goes right. You end up with a clean, flat finish that doesn't usually require much, if any, shaving or grinding. If you're working on the outer skin of an aircraft, that flush finish is pretty important for aerodynamics.
Why We Still Use Them
You might wonder why we don't just use solid rivets everywhere. Solid rivets are cheaper and arguably even stronger. The problem is accessibility. To set a solid rivet, you need a person with a rivet gun on one side and another person (or a very long arm) holding a bucking bar on the other.
In a lot of modern aircraft designs, you simply can't get to the back side of the panel. You might be closing up a fuel tank or attaching a skin to a rib where there's no physical way to reach inside. That's where the cherrylock rivet earns its keep. It gives you the structural integrity of a solid fastener without needing a "bucker" on the inside. It's a huge time-saver, and in many repair scenarios, it's the only viable option.
Strength and Vibration
One of the biggest enemies of any mechanical joint is vibration. Think about an engine cowling or a wing tip. Those parts are constantly shaking, buzzing, and flexing. A cheap rivet will eventually "smoke"—that's when the rivet gets loose and starts vibrating in the hole, creating a fine black aluminum oxide dust that looks like smoke streaks.
A properly installed cherrylock rivet doesn't do that. Because the stem is mechanically locked into the sleeve, it acts like a single solid piece of metal. It handles the cycles of tension and shear without loosening up. Honestly, if you see "smoking" rivets on a plane, it's a sign that someone used the wrong fastener or did a poor job on the installation.
Knowing Your Varieties
Not all cherrylocks are created equal. You've got different head styles, materials, and sizes. The two most common head styles you'll see are the "universal head," which sits on top of the metal like a little button, and the "countersunk head," which sits flush with the surface.
Then you have to consider the material. Most are made of aluminum alloys, but you'll also find them in Monel or stainless steel for areas that get hot or need extra corrosion resistance. Choosing the right one is usually a matter of following the structural repair manual (SRM), but it's good to know why you're picking one over the other. If you put an aluminum rivet in a high-heat zone near an exhaust, you're going to have a bad day eventually.
Bulbed vs. Wired
You'll often hear techs talk about "bulbed" cherrylocks. These are specifically designed for thinner sheets of metal. When you pull them, the backside of the rivet "bulbs" out into a wider footprint. This spreads the load over a larger area so the rivet doesn't just pull straight through the thin skin. It's a clever bit of engineering that makes the cherrylock rivet incredibly versatile across different parts of the airframe.
A Few Tips for Success
If you're new to using these, there are a few things that can trip you up. First, hole preparation is everything. If your hole is even a tiny bit too big, the rivet won't fill it properly, and the mechanical lock might not engage correctly. Use a sharp drill bit and don't "wobble" the drill.
Second, check your grip length. Every cherrylock has a specific range of thickness it can fasten. If your grip is too short, the lock won't set. If it's too long, the stem might break off high, leaving a jagged edge that's a pain to fix. I always keep a grip gauge in my pocket. It's a simple little tool that saves you from wasting expensive fasteners.
Lastly, take care of your pulling tools. The jaws inside those pneumatic guns get dirty and worn down. If the tool starts slipping on the stem, don't just keep trying to pull it. Stop, clean the jaws, and make sure everything is lubed up. A slipped pull can mar the skin of the aircraft, and that's a whole different headache you don't want to deal with.
Final Thoughts
It's easy to get caught up in all the high-tech stuff in modern manufacturing, but the cherrylock rivet proves that sometimes the classic solutions are still the best. They are reliable, incredibly strong, and they solve the "one-side-access" problem perfectly.
Next time you're looking at a vintage Cessna or even a modern bush plane, take a close look at the fasteners. If you see those perfectly flush stems with a tiny circular ring around the center, you're looking at the workhorse of the aviation world. They might be small, but they're doing the heavy lifting to keep everything held together when it matters most. Using them correctly takes a bit of practice and the right gear, but once they're in, you can pretty much forget about them—and that's exactly what you want from a fastener.