Minimum Wall Thickness for CNC Parts
Minimum and recommended wall thickness for aluminium, steel, stainless, titanium, copper and plastics — plus wall height limits and fixturing for thin walls.
Minimum and recommended wall thickness by material
| Material | Absolute minimum | Recommended | What happens if it is too thin |
|---|---|---|---|
| Aluminium (6061, 7075) | 0.5 mm | 1.0 mm | Chatter during finishing, the wall pushes away from the cutter, the dimension goes out of tolerance. |
| Steel (1045, 4140) | 0.8 mm | 1.5 mm | Tool deflection at 0.5 mm is severe with steel and walls bow inward. Harder steels amplify this. |
| Stainless steel (304, 316) | 0.9 mm | 1.5 mm | Stainless work-hardens rapidly. Thin walls overheat, warp and may crack, and tool wear accelerates. |
| Titanium (Ti-6Al-4V) | 1.0 mm | 1.5 mm | Titanium has low thermal conductivity, so heat builds up in thin sections and causes thermal warping. |
| Copper and brass | 0.5 mm | 0.8 mm | The soft material helps and copper can go quite thin, but very thin copper walls are fragile during handling and assembly. |
| Engineering plastics (Delrin, Nylon, PEEK) | 0.4 mm | 0.8 mm | Plastics deflect under cutting force and thin walls flex away from the tool, producing burrs and poor accuracy. |
How to read this table. The absolute minimum is the thinnest wall that can be machined without the tool breaking or the wall deflecting out of tolerance. The recommended value is what we quote from, because it leaves room for the deflection you actually get in production.
How Tall a Wall Can Be
Thickness alone does not decide whether a wall holds. A 1 mm wall 3 mm tall is fine; the same wall 30 mm tall is a cantilever beam that vibrates during machining.
| Rule | Guideline | Why it matters |
|---|---|---|
| — | Wall thickness at least 1/5 of the adjacent feature height | A tall thin wall behaves like a cantilever beam. |
| — | Maximum unsupported height = 8× wall thickness in aluminium, 5× in steel | Beyond this ratio the wall vibrates during machining. |
| — | Keep walls within 20% of each other on the same part | Uneven walls cause differential cooling in heat treatment and uneven stresses. |
| — | Gradual transitions between thick and thin sections | Abrupt thickness changes create stress concentrators. Add a fillet or taper. |
| — | Rib thickness = 0.6× wall thickness, rib height at or below 5× rib thickness | Thick ribs create sink marks on the opposite surface. |
What a Tight Wall Costs
Tightening a wall specification is one of the cheapest ways to raise a part's price without changing its function. These are the multipliers we see.
| Design feature | Standard specification | Tight or difficult specification | Cost multiplier |
|---|---|---|---|
| Wall thickness (aluminium) | at least 1.0 mm | 0.5–0.8 mm | 1.3–1.8× |
| Wall thickness (steel) | at least 1.5 mm | 0.8–1.2 mm | 1.4–2.0× |
| Internal fillet radius | R3–R6 mm | R0.5 mm or smaller | 1.8–3.0× |
| Floor radius in pocket | R1–R3 mm | R0 (sharp) | 3.0–5.0× |
| Edge break | 0.5 mm chamfer (default) | Sharp edges, no break | 1.0×, but higher handling risk |
| External radius | Sharp or 0.5 mm break | Large cosmetic radius, R5 and above | 1.1–1.3× |
| Deep pocket aspect ratio | depth at or below 4× width | depth above 6× width | 1.5–2.5× |
| Tall thin wall | height at or below 5× thickness | height above 8× thickness | 1.5–2.0× |
How to Hold a Thin Wall While Machining
A thin wall is mostly a fixturing problem. The right support method lets the shop cut the wall at its minimum thickness instead of the recommended one.
| Fixturing method | Minimum wall thickness | Material compatibility | Typical deflection | Best use |
|---|---|---|---|---|
| Hard jaws (standard) | at least 6 mm | All metals | 0.1–0.3 mm | Thick parts only |
| Soft jaws (machinable) | at least 1.5 mm | All metals | 0.02–0.05 mm | General thin walls |
| Vacuum chuck | at least 0.3 mm (foil) | Non-porous, any metal | 0.01–0.03 mm | Flat sheet, light cuts |
| Magnetic chuck | at least 1 mm | Ferromagnetic only | 0.02–0.08 mm | Steel ground plates |
| Wax potting | at least 0.5 mm | All metals, avoid thermal exposure | 0.01–0.05 mm | Thin-wall roughing |
| Low-melt alloy | at least 0.5 mm | All metals, check thermal history | 0.005–0.02 mm | Complex thin-wall cavities |
| Sacrificial tabs or bosses | Any, by design | All metals | Effectively zero | The best general answer |
How to Use These Numbers
- Quote the recommended value, not the absolute minimum. The absolute minimum is what the tool can physically cut; the recommended value is what holds dimension in production.
- Wall thickness is about height as much as section. A 1 mm wall that stands 30 mm tall is out of spec even though the thickness looks fine on the drawing.
- The real minimum is often set by the fillet, not the wall. A 0.6 mm wall with an R0.5 internal corner is unmachinable — the tool cannot reach the corner. Add sacrificial tabs or boss the wall.
- Surface finish and coating eat into a thin wall. Anodize adds roughly 25 µm per side, so a 0.6 mm nominal wall is 0.55 mm after coating. Account for it in the tolerance stack.
- If the wall has to be thin, say so on the drawing and tell us how it will be fixtured. We will quote the support method (soft jaws, sacrificial tabs, vacuum) rather than silently up the wall thickness.
Frequently Asked Questions
What is the minimum wall thickness for aluminium?
0.5 mm is the absolute minimum for 6061 and 7075, and 1.0 mm is what we recommend for production. At 0.5 mm the wall pushes away from the cutter and the dimension drifts out of tolerance; at 1.0 mm it holds. Thin aluminium walls also need sacrificial tabs or soft jaws.
0.5 mm is the absolute minimum for 6061 and 7075, and 1.0 mm is what we recommend for production. At 0.5 mm the wall pushes away from the cutter and the dimension drifts out of tolerance; at 1.0 mm it holds. Thin aluminium walls also need sacrificial tabs or soft jaws.
What is the minimum wall thickness for stainless steel?
0.9 mm absolute, 1.5 mm recommended. Stainless work-hardens rapidly, so a thin wall overheats, warps and can crack, and the tool wears much faster than on mild steel.
0.9 mm absolute, 1.5 mm recommended. Stainless work-hardens rapidly, so a thin wall overheats, warps and can crack, and the tool wears much faster than on mild steel.
Why does the recommended thickness differ from the absolute minimum?
The absolute minimum is the thinnest wall the cutter can physically hold without breaking. The recommended value leaves room for the deflection that actually happens in production — clamping force, tool deflection and thermal growth. Quote from the recommended value.
The absolute minimum is the thinnest wall the cutter can physically hold without breaking. The recommended value leaves room for the deflection that actually happens in production — clamping force, tool deflection and thermal growth. Quote from the recommended value.
How tall can a thin wall stand?
Keep the wall thickness at least 1/5 of the adjacent feature height, and cap the unsupported height at 8× the wall thickness in aluminium and 5× in steel. Beyond that the wall behaves like a cantilever beam and vibrates during machining.
Keep the wall thickness at least 1/5 of the adjacent feature height, and cap the unsupported height at 8× the wall thickness in aluminium and 5× in steel. Beyond that the wall behaves like a cantilever beam and vibrates during machining.
Does anodizing reduce the wall thickness?
Yes — anodizing adds roughly 25 µm per side, so a 0.6 mm nominal wall comes out at about 0.55 mm. On a thin wall that can consume a meaningful share of the tolerance. Specify the coating before the final wall dimension, or add the allowance to the drawing.
Yes — anodizing adds roughly 25 µm per side, so a 0.6 mm nominal wall comes out at about 0.55 mm. On a thin wall that can consume a meaningful share of the tolerance. Specify the coating before the final wall dimension, or add the allowance to the drawing.
Standards & Sources
- Site article: /news/minimum-wall-thickness/ — the long-form guide, including machining thin walls without moving them
- Site page: /wiki/dfm/thin-wall-machining-deformation/ — design for manufacturing rules that interact with wall thickness
Related Pages
- /news/minimum-wall-thickness/ — The long-form guide: why there are two numbers, and how to machine a thin wall without moving it
- /wiki/dfm/thin-wall-machining-deformation/ — DFM rules that interact with wall thickness, fillet radii and pocket depth
- /wiki/reference/standard-tolerances/ — General tolerances for the thin-wall feature itself
- /resources/dfm-guide/ — DFM checklist to run against a drawing before quoting