Guides / Process
Thin Wall Titanium: What Is Routine, What Is Expensive and What to Avoid
Wall thickness is the fastest way to move a titanium price, in either direction. Buyers often treat it as a design detail. Shops treat it as the first thing they look at.
The ratio matters more than the number
The question is never just “how thin”. It is how thin relative to how tall, and how well it can be supported while it is being cut.
| Wall height to thickness | Difficulty | What the shop does |
|---|---|---|
| Up to 5 to 1 | Routine | Normal roughing and one finishing pass |
| 5 to 1 up to 10 to 1 | Moderate | Lighter finishing passes, climb milling, leave the wall until last |
| 10 to 1 up to 15 to 1 | Hard | Support material or tabs, staged removal, possibly a stress relief |
| Above 15 to 1 | Specialist | Bespoke fixture, wax or low melt support, multiple light passes |
A 2 mm wall 10 mm tall is a 5 to 1 wall and nobody blinks. A 1 mm wall 30 mm tall is 30 to 1 and belongs in a conversation before the drawing is signed.
Why titanium is worse than aluminium here
Three things stack up.
Cutting force. Titanium needs a real chip load to cut rather than rub, and that means force pushing sideways on the wall.
Modulus. Grade 5 sits around 114 GPa, well below steel. The wall deflects, then springs back after the cutter passes, so the wall finishes thicker than programmed unless the shop compensates.
Heat. With thermal conductivity around 7 W/m K the heat has nowhere to go. A thin wall has very little mass to absorb it, so it grows while it is being cut and shrinks afterwards.
The result is a wall that is out of tolerance in a way that is hard to predict from the programme alone. Shops deal with it by measuring, adjusting and taking another pass, which is exactly the time that shows up in the quote.
What a shop actually does
- Leave the thin feature until last, so it is supported by material for as long as possible.
- Rough both sides progressively rather than finishing one side and then attacking the other.
- Sacrificial tabs or ribs left in during machining and removed at the end, sometimes by hand.
- Support material: wax, low melt alloy or a machined backing block clamped behind the wall.
- Light finishing passes, often 0.1 mm or less radial, sometimes two or three.
- Climb milling on finishing, to push the cutting force into the material rather than pulling the wall.
- A stress relief between roughing and finishing where the part shape invites distortion.
Each of those is a decision that has to be made once, for your part, by a person. That is why thin wall titanium parts have a high one time cost and why quantity helps more than usual.
Design moves that get the price back
Ask whether the wall needs to be that thin. Half a millimetre of extra wall often costs nothing in weight and saves a fixture.
Add a rib or a flange. A small stiffening feature at the top of a tall wall changes the whole job, because the wall stops behaving like a cantilever.
Keep the wall uniform. A wall that steps from 3 mm to 1 mm mid height needs two strategies instead of one.
Open the internal corners. A bigger corner radius lets the shop use a stiffer cutter, which cuts the deflection problem at the source.
Avoid a thin wall next to a tight tolerance. If both are unavoidable, say which one is the real requirement.
Ask about a different stock form. If the part is essentially a thin walled tube with features, starting from tube instead of solid bar can remove most of the problem and most of the material cost.
What to say on the RFQ
Call out the thin feature explicitly rather than leaving the shop to find it. One line is enough.
Thinnest wall 1.2 mm, 28 mm tall, on the left face. Wall thickness tolerance ±0.1 mm, flatness is not critical.
That tells a shop three things it would otherwise have to assume: where the hard feature is, how tight it really is, and what it can relax. Quotes come back both faster and lower when that line is present.
When to walk away from the geometry
Some thin wall titanium parts should be made another way. If the part is essentially a thin shell, consider whether it should be:
- Machined from tube or a forging rather than solid.
- Split into two parts and joined.
- Made in Grade 2 instead of Grade 5, which deflects a little less obligingly but cuts far more easily.
- Made in a different material altogether, if the thin wall was a weight saving measure and titanium already gave you the weight saving.
A shop that cuts titanium every week will raise these on its own. If nobody raises them, that is worth noticing.
Frequently asked questions
What is the thinnest wall you can machine in titanium?
Shops regularly hold around 0.8 to 1 mm on short walls and specialists go well below that on aerospace work. The useful limit is not a number, it is the ratio of height to thickness. A 1 mm wall 10 mm tall is routine, the same wall 60 mm tall is a different job.
Why does a thin wall cost so much more in titanium than in aluminium?
Cutting forces are higher, the material springs back and the wall cannot be cooled through the section. That means lighter passes, more of them, and usually a fixture built for the part rather than a vice. All of that is time somebody has to pay for.
Does wall thickness affect the tolerance I can hold?
Yes, directly. A ±0.02 mm tolerance on a solid boss is routine. The same tolerance on a 1 mm wall standing 40 mm tall may be genuinely impossible without a support fixture, and it should be discussed before the drawing is released.
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