Choosing a Rivet Gun: 2X, 3X and 4X Explained

The X number on a rivet gun is the single most confusing piece of nomenclature a new sheet metal worker meets, largely because it looks like it should be a size and behaves like a class.

What the number means

It is a rating of hitting power and speed together, and the two move in opposite directions. A higher number means a heavier hammer striking more slowly. A lower number means a lighter hammer striking faster.

Nearly every aviation gun takes a 0.401 inch shank, which is what your rivet sets fit, so sets are interchangeable across the range. That matters when you own more than one gun.

Why fast and light is not the same as gentle

The intuition most people arrive with is that a faster gun is more aggressive. It is the other way round for the thing that matters.

A rivet is set by driving the shank until the shop head forms. What damages the work is not the number of blows but the energy in each one relative to the material. A 2X delivers many light blows, which gives you time to see what is happening and stop. A 4X delivers few heavy ones, and on 0.5 mm skin the first blow has already done something you cannot undo.

The other half of it is work hardening. Too many light blows on aluminium hardens the material around the hole, which is why a 2X on 1/8 inch rivets is not a substitute for a 3X even though it will eventually set them. The rule of thumb: use the gun that sets the rivet in a small number of controlled blows, which usually means three to five.

Which one to buy first

Buy the 3X. It covers 3/32 inch and 1/8 inch solid rivets, which is the great majority of airframe riveting in aluminium: wing skins, fuselage panels, ribs, stringers, most kit aircraft.

The 3X in our catalogue is 178 EUR ex VAT. The 2X is 148 EUR and the 4X is 219 EUR, and neither is the one to own on its own.

Buy the 2X second if you do a lot of thin skin work or you are teaching. Buy the 4X second if your work includes heavier structure or stainless fasteners. If you know you will end up with all three, a riveting kit pairing the three guns with bucking bars and sets costs less than buying them one at a time as each job demands.

What the gun does not come with

Three things people are surprised by.

Rivet sets. Ordered separately, because the set you need depends on the rivet head rather than on the gun. Universal heads need a universal set, flush rivets need a swivel flush set. See rivet sets.

A bucking bar. The gun forms nothing on its own. The bar is what makes the shop head, and choosing one is its own decision, covered in bucking bars by weight and profile.

A regulator. Gun pressure is how you actually control the blow, and setting it from a shop line with no regulator at the bench is guesswork. Start low, around 2 bar, and come up until the rivet sets in a few blows.

Squeeze it if you can reach it

The most useful thing an experienced sheet metal worker will tell a beginner: if you can get to both sides of the rivet, squeeze it rather than shoot it. One controlled squeeze produces a more consistent shop head than any number of blows, marks nothing, and does not require ear defenders. A hand squeezer will set more of your rivets than the gun will, on most builds.

The gun is for the rivets you cannot reach, which is exactly why it is worth learning to use properly rather than avoiding.

Where the gun lives afterwards

A rivet gun, four bucking bars and a dozen sets is a drawer that either has a home for each item or turns into a pile. That is not a moral point, it is a FOD one: loose sets in a drawer end up on a hangar floor and eventually somewhere worse. If the kit travels to an aircraft, it is worth cutting shadow foam for it, so a missing set is visible before the box closes rather than after.