Carbon Fiber Tube Wall Thickness: How to Choose
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The number is smaller than you think
Ask most people what wall thickness they want in a carbon fiber tube and they'll say 2mm. It sounds structural. It's the figure that turns up in forum posts and in a lot of supplier copy, including some of ours.
Across 1,916 units where I could work the wall out from the outside diameter and the bore, 1mm is the answer 45 percent of the time. 2mm comes second at 23 percent. Half a millimetre, which sounds like a novelty, does 5 percent.
So the honest starting point is thinner than the conventional answer. There's a reason for that, and there's a set of cases where the conventional answer is right. Both are worth knowing, because picking the wrong wall is the most expensive mistake you can make on a tube — you either get something that flexes under load or something unnecessarily heavy, and you find out after it's cut and drilled.
What we've actually shipped
| Wall | Units | Share |
|---|---|---|
| 0.5mm | 102 | 5.3% |
| 1mm | 857 | 44.7% |
| 1.5mm | 390 | 20.4% |
| 2mm | 429 | 22.4% |
| 2.5mm | 33 | 1.7% |
| 3mm | 80 | 4.2% |
A tall spike at 1mm, a broad shoulder from 1.5 to 2mm, and thin tails either side. Below 0.5mm we don't make anything, and above 3mm the volume is essentially zero.
The mistake is thinking about wall on its own
Here's the pattern that took me longer to notice than it should have.
Wall thickness by itself tells you almost nothing. What matters is wall in relation to diameter. A 1mm wall on an 8mm tube is an eighth of the diameter, which is chunky. The same 1mm on a 24mm tube is a twenty-fourth, which is a stiff shell with almost no material in it.
Our order data shows this clearly. Look at which wall people pick for which diameter:
| Outside diameter | Units | Most common wall | Share |
|---|---|---|---|
| 8mm | 207 | 1mm | 73% |
| 10mm | 123 | 1mm | 76% |
| 12mm | 75 | 1mm | 65% |
| 24mm | 50 | 1mm | 90% |
| 22mm | 238 | 1.5mm | 84% |
| 32mm | 49 | 1.5mm | 57% |
| 16mm | 100 | 2mm | 40% |
| 30mm | 64 | 2mm | 41% |
| 40mm | 68 | 2mm | 38% |
| 20mm | 104 | 3mm | 42% |
Read down the wall column: 1mm, 1mm, 1mm, 1mm, then 1.5, 1.5, then 2, 2, 2. The wall climbs as the diameter climbs. That isn't people being conservative. It's people arriving at roughly the same stiffness by two routes.
Bending stiffness goes up very steeply with diameter — roughly with the fourth power — and only linearly with wall. So doubling the diameter gives you a much bigger stiffness gain than doubling the wall, and it does it while moving material away from the neutral axis rather than piling it on. A 24mm tube at 1mm wall and a 16mm tube at 2mm wall land in a similar place structurally, and the 24mm one weighs less.
That's why 90 percent of our 24mm sales are the thin wall. Buyers have worked out that they can have a bigger, stiffer tube for less weight by going up a size rather than up a wall.
What each band is for
0.5mm. Light and fragile. It dents with a thumbnail and a clamp will flatten it if you do the bolts up hard. There is a market for it — 5 percent of our volume — and it's people who know exactly what they're building and have decided the weight matters more than the durability. Not a first purchase.
1mm. The default, and for good reason at 8mm to 14mm outside. Stiff enough to hold a load over a short span, light enough that nobody counts grams, and forgiving enough to survive ordinary handling. If you have no strong reason to go elsewhere, this is where to start.
1.5mm. What our 22mm buyers overwhelmingly choose, and a sensible middle. Noticeably more resistant to dents and crushing than 1mm without the weight of a 2mm wall. If your part will be clamped and you don't want to fuss with sleeves, this is a comfortable place to be.
2mm. Structural. This is the wall for long spans, real loads, robot arms and anything that has to shrug off impacts. It's also what most people default to before they've done the arithmetic, which is why it holds 22 percent of volume rather than something higher.
3mm. Rare, and almost all of it is one specification — 20mm outside, 14mm bore. That's a part with a small bore and a lot of material around it, which tells you buyers are using it where the tube itself is the structure, or where crushing and hole-bearing matter more than weight. It is not a typical airframe choice.
When thin walls bite you
Model aircraft are a large share of what we ship, and they follow their own logic — spars want a large diameter at a thin wall, pushrods want pultruded rather than roll wrapped. There is a guide to that specifically.
There's one failure mode specific to thin walls, and it catches people on their first build.
A clamp closing on a 0.5mm or 1mm wall has nothing resisting it from the inside. The wall deflects inwards as you tighten, the tube goes oval at that point, and you can feel it go soft before the bolt is actually tight. Carry on and you'll crack it.
Two fixes. The cheap one is a reinforced sleeve pushed into the tube end, so the clamp is squeezing aluminium instead of unsupported carbon. A couple of dollars and it solves the problem completely. The other is to go up a wall at the clamped section and accept the weight.
The failure mode specific to thick walls is different and less dramatic: you've spent weight you didn't need to. On a drone arm that's flight time you paid for and didn't get. It won't break, it just underperforms, which is harder to notice and therefore easier to live with by mistake.
How to decide, in order
Work out the span and the load first, not the wall. How far apart are the supports, and what's hanging off it.
Then choose the diameter to handle the stiffness you need. Going up a size is almost always better value than going up a wall.
Then choose the thinnest wall in that diameter that still holds. At 8mm to 14mm that's usually 1mm. At 16mm and above, 1mm or 1.5mm. Above 25mm, 1.5 to 2mm.
Then ask whether anything is going to squeeze it. A clamp, a bolt through a hole, or a hard landing. If yes, either step up a wall or plan a sleeve.
Then check the weight. If you've ended up at 2mm and the diameter is doing the work, try going down a wall and see whether the numbers still stack up. A surprising share of our customers would be fine a step thinner than they ordered.
What the data can't tell you
The distribution above is our customer base, and it leans toward model aircraft, drones and small engineering jobs. Nothing here is a survey of the industry.
It also can't tell you what the right wall is for your build. Every row in that first table is a record of someone else's decision, and someone else's decision doesn't know how far your supports are apart. Use this to understand why the common answers are common. Don't use it to skip the arithmetic.
And a few large trade orders sit inside the numbers — 20mm at 3mm wall is a good example of a figure driven by a handful of buyers rather than a broad trend.
Frequently asked
Is 1mm wall strong enough?
For a short span with a light load, yes, and it's what most of our customers use. "Strong enough" is really a question about span and load. A 1mm wall tube on a 300mm drone arm is working comfortably. The same tube spanning a metre with a weight in the middle is not.
What's the thinnest wall I should buy?
0.5mm, and only if you know why. It's 5 percent of what we sell and none of those buyers are guessing. A clamp on a half-millimetre wall without a sleeve will crush it, and so will a tight thumb.
Why does a thicker wall not make the tube much stiffer?
Because stiffness in bending depends far more on how far the material is from the centreline than on how much of it there is. Wall adds material linearly; diameter adds it to the fourth power. That's why moving up a diameter beats moving up a wall almost every time, and usually weighs less.
Does wall thickness affect the outside diameter I need?
No, and this is the useful part. Outside diameter is set by whatever the tube fits into — clamp, cap, or drilled hole. Wall and bore are then free variables inside that constraint. Pick the outside diameter from the fitting, then choose wall from the load.
Can I mix walls in one assembly?
You can, and it's often sensible. Thicker tube at the root where bending moments peak, thinner out at the tip where they're small, is how a lot of well-designed arms are built. It's more parts to keep track of and more cutting, so most people use one wall for simplicity.
Tubes are grouped by outside diameter in the carbon fiber tube sections, with the bore options on each product page. For how outside diameter, bore and wall relate, the sizing guide works through it. If you tell us the span and the load, we'll suggest a wall rather than leave you to guess.