You ever grab a rivet set, line up on an MS20470, and end up with a shop head that looks like it lost a fight? Yeah. Me too. The weird part is, it's rarely the rivet's fault That's the part that actually makes a difference..
Here's the thing — a rivet set used to drive MS20470 rivets should be matched to the job in ways most beginners (and honestly, a lot of pros) never stop to think about. So get it wrong and you're peening the wrong way, bruising the skin, or setting heads that don't meet spec. Get it right and the work looks like it came off a production line Not complicated — just consistent..
So let's talk about what actually matters when you're standing there with a bucking bar in one hand and a pneumatic hammer in the other.
What Is An MS20470 Rivet And Why The Set Matters
MS20470 is the military spec for a universal head solid rivet. You've seen them everywhere — aircraft skins, brackets, anything that needs a permanent mechanical joint and can't afford a loose fastener. The head is rounded, low-profile, and designed to spread load without digging into the material.
Now, the rivet set — sometimes called a rivet gun tip or driving anvil — is the part that actually touches the rivet head. Because of that, a rivet set used to drive MS20470 rivets should have a slightly concave face that cups the universal head without slipping off. In real terms, if the cup is too deep, you'll crush the head. Too shallow, and the set rides up and scars the surrounding aluminum.
The Universal Head Geometry
The MS20470 head isn't a dome like an AN470's older cousins or a countersunk flush head. It's a broad, gentle curve. That means the set's dimple needs to match that curve close enough to center itself on every shot. In practice, most sets sold for MS20470 work are radius-matched to the head diameter, not the shank.
Material Of The Set
Good sets are hardened tool steel, sometimes chrome-plated to resist peening on the face. Cheap ones mushroom on the tip after a few dozen rivets. And once the set face distorts, it transfers that damage straight to your rivet head No workaround needed..
Why It Matters
Why does this matter? Because a bad set doesn't just make ugly rivets — it makes non-airworthy rivets.
On an aircraft, an MS20470 with a shop head that's too thin or too fat fails inspection. 5x the shank, height between 0.Practically speaking, 3x and 0. 13: shop head diameter should be 1.That's why the FAA and most repair stations go by AC 43. Plus, a rivet set used to drive MS20470 rivets should help you hit that every time without thinking. Day to day, 6x the shank. If the set is wrong, you'll fight the gun, the bucking bar, and the metal all at once.
And outside aviation? A loose rivet in a trailer panel rattles. Same principle, smaller consequences. A smashed head on a bike frame looks like crap and can start a crack Not complicated — just consistent..
Turns out the set is the cheapest part of the system and the easiest to blame when everything else is set up fine And that's really what it comes down to..
How It Works
Driving a solid rivet is simple to describe and annoying to master. The gun pushes the set into the manufactured head. Plus, the bucking bar behind the shop head reflects the energy. The shank expands, fills the hole, and the excess length squishes into a second head.
But the set is doing more than transmitting force. It's locating the rivet, protecting the skin, and controlling how the metal flows.
Picking The Right Set Diameter
A rivet set used to drive MS20470 rivets should be sized to the rivet head, not the hole. Practically speaking, a 3/32 MS20470 takes a different set face than a 1/8 or 5/32. Now, using a too-big set means the edge of the set hits the skin before it seats on the head. That leaves a ring dent around every rivet — called "skin marking" and a real headache on a visible surface.
Concavity And Contact
The face of the set should contact the rivet head on the curved surface, not the flat top rim. If it only touches the rim, the head cracks or the set slips. The slight cup centers the set so each hammer blow lands square. In practice, a well-matched set will "stick" to the rivet head between shots because the vacuum of the cup holds it.
No fluff here — just what actually works Most people skip this — try not to..
Gun Pressure And Stroke
Even with the right set, you need the right air pressure — usually 80–90 psi for light riveting, less for small MS20470 sizes. Too much and the set bounces, peening the head into a mushroom. So too little and you're hammering forever. The set should never be the only thing absorbing shock; the bucking bar does the real work Which is the point..
Bucking Bar Sync
Here's what most people miss: the set and bar are a pair. Small rivets, small bar. Big rivets, bigger bar. A rivet set used to drive MS20470 rivets should be paired with a bar heavy enough to match the rivet. If the bar is too light, the set does the deforming and you get a beaten manufactured head.
Common Mistakes
Honestly, this is the part most guides get wrong — they tell you to "just buy a rivet set" and move on.
One mistake: using a flush set on a universal head. Flush sets are flat or near-flat for dimpled skins. Put that on an MS20470 and you'll flatten the round head into a pancake. Not acceptable.
Another: grinding the set face to "fix" it. Once you grind a set, you change the radius and the hardness. It might work for one size, then wreck the next batch.
And the classic — using one set for every rivet on the bench. A rivet set used to drive MS20470 rivets should stay with MS20470 sizes. Mix it with AN426 or cherry rivets and you'll round off edges you can't see until inspection Not complicated — just consistent..
I know it sounds simple — but it's easy to miss that a set with a chipped face is worse than no set at all. You'll swear the gun is broken. It isn't.
Practical Tips
What actually works on the bench?
Keep a dedicated set per rivet family. Day to day, label them with a paint pen. MS20470 3/32 gets its own, 1/8 gets its own. Sounds obsessive until you've ruined a skin Still holds up..
Before you start a job, test-set on a scrap pair of aluminum sheets. Look at the manufactured head after three shots. Now, if it's clean and centered, the set is good. If it's marked, stop Most people skip this — try not to. Simple as that..
Wipe the set face with a light oil between sessions. Rust on the cup transfers to rivet heads and looks like corrosion later.
And don't death-grip the gun. A rivet set used to drive MS20470 rivets should be held lightly enough that it follows the rivet, not forced. Forcing it is how you get sideways hits and bent sets.
Real talk — spend the extra twenty bucks on a name-brand set from a aviation supplier. The Harbor Freight special will cost you more in rejected rivets Most people skip this — try not to..
FAQ
What size rivet set for MS20470 1/8 rivets? You want a set with a cup matched to the 1/8 universal head diameter, typically listed as a 1/8 MS20470 set. The shank of the set should fit your gun's retainer — usually 0.401 or 0.515 inch That's the whole idea..
Can I use the same set for MS20470 and countersunk rivets? No. Countersunk rivets need a flush or dimple set. A universal head set will not seat a flush rivet and will damage the skin around it.
How do I know my rivet set is worn out? Look at the face under good light. If the cup is shallow, cracked, or the edge has rolled, it's done. Also, if every rivet comes out with a ring around it, the set is telling you something.
Do I need different sets for aluminum vs steel MS20470? The head shape is the same, so the set geometry doesn't change. But steel rivets need more force, so a heavier-duty set that won't deform under harder hits is smart
if you're driving steel regularly Most people skip this — try not to..
Should I replace both the set and the gun if rivets keep failing? Start with the set. Nine times out of ten, a chipped or wrong-profile set is the culprit. Swap it, re-test on scrap, and only look at the gun if the new set still produces bad heads.
Is it worth keeping old sets for "rough" work? Only if they're kept clearly separate and used on non-structural or shop-made fixtures. Never let a worn set drift back onto aircraft skins — that's how a casual mistake becomes a logged discrepancy Simple, but easy to overlook..
Conclusion
Rivet sets are cheap insurance against expensive rework. Match the set to the rivet family, keep them labeled and clean, and trust what a test panel tells you before you ever touch a finished surface. Day to day, a worn or wrong set won't announce itself with a bang — it shows up later as a rejected inspection or a head that doesn't look right under a magnifier. Treat the set like the precision tool it is, and your rivets will speak for themselves Less friction, more output..
