Wall Thickness Guidelines for CNC Parts

What’s the minimum wall thickness for CNC machining?

If you’re asking that, you’re already doing better than most. Because wall thickness isn’t just a geometric property—it’s a major risk factor in part failure, chatter, cost overruns, and even quote rejections.

At Ekinsun, we’ve seen everything from razor-thin walls that cracked during deburring, to overbuilt designs that drove up weight and cost for no real reason. Let’s talk about how to get it right—based on real machining experience.

Why Minimum Wall Thickness Matters More Than You Think

There’s a temptation in CAD to push limits. Ultra-thin walls look cool. Lightweight parts feel efficient. But once it hits the CNC shop floor?

Vibration ruins finishes

Cutting pressure causes wall flex

Thin sections break in cleaning or anodizing

And in many cases, thin walls don’t even save material—they just waste machining time.

Technical diagram showing CNC wall thickness guidelines, featuring an L-shaped machined part with labeled arrows indicating wall height and thickness, suggesting a maximum 5–6× wall height-to-thickness ratio.

Engineering-Based Wall Thickness Guidelines

Let’s get specific. Based on real-world jobs and cross-verified supplier specs (Protolabs, JLCPCB, 3ERP), here’s what works:

| Material | Recommended Min Wall Thickness | Critical Notes |

| ----------------- -- | ------------------------------ | ------------------------------------------------ |

| **Aluminum** | 0.8–1.0 mm | Avoid >5:1 height/thickness ratio |

| **ABS / Delrin** | 1.2–1.5 mm | Good stiffness, poor vibration tolerance |

| **Nylon / POM** | 1.5–2.0 mm | Tends to bend—watch tall ribs |

| **Stainless Steel** | ≥ 1.0 mm | Hard to cut, needs cooling margin |

| **Brass / Copper** | 0.8 mm | Burr-prone—use light cuts |

Tip: A “machinable” wall doesn’t mean a “usable” one. Parts still need to be cleaned, handled, and assembled—don't design right to the edge of possibility.

How Wall Thickness Affects CNC Reality

What happens if you push the limits?

Thin walls vibrate, leading to inconsistent tool paths

Walls deflect, especially under side-milling

Heat builds up—especially in metals like stainless

Fragile edges chip during post-processing

And if you’re planning for anodizing or bead blasting? You’ll lose another 0.02–0.05 mm surface layer—potentially enough to destroy tolerances.

A Real Case: When “0.6 mm Wall” Became a Costly Mistake

One client submitted a sleek black Delrin shell—walls just 0.6 mm thick, 40 mm tall.

We knew right away this was trouble:

During finishing, the walls flexed visibly.

After ultrasonic cleaning, 20% of parts cracked at the corners.

The fix? A quick redesign to 1.2 mm walls + internal ribs. No failures since.
(Insert a Before vs After illustration here — ALT: Thin vs reinforced CNC wall design comparison)

Side-by-side comparison of CNC-machined Delrin parts: the left model shows a thin-walled part with cracks, while the right features a redesigned version with thicker walls and internal reinforcing ribs to prevent failure.

Design Smarter: 5 Key Tips for Machinable Thin Walls

Avoid height > 5–6× wall thickness — It’ll flap under the cutter
Add ribs — Just a 1mm gusset makes a huge difference
Support corners with fillets — Sharp edges = stress risers
Discuss edge cases with your machinist — They’ll tell you what’s realistic
Plan for handling — Especially during finishing and inspection

Some users find success using wall stiffening strategies similar to injection molding—those ideas apply surprisingly well in CNC too.

Frequently Asked Questions (FAQ)

Q: What’s the thinnest wall I can get away with in aluminum?
A: Technically, we’ve machined walls down to 0.6 mm—but only on small, low-height features. For repeatable results, stick to ≥0.8 mm.

Q: Will polishing or anodizing damage thin walls?
A: Yes—anodizing adds/removes surface layers, which can create cracking or visible distortion if wall thickness is too thin.

Q: Can I reduce cost by making walls thinner?
A: Usually not. Thinner walls take longer to cut, need more cautious feeds, and often result in higher scrap rates.

Q: What if I need a light part?
A: Instead of thinning walls, try hollowing thick areas with internal cutouts or lightening pockets—those are safer to machine.

Add This to Your Checklist

Before exporting your next STEP file, ask yourself:

Are all vertical walls thick enough to resist tool pressure?

Do I have internal ribs where height gets tall?

Can this part survive deburring, cleaning, and finishing?

If in doubt, simulate it—or send it to us. We’ve caught thousands of avoidable wall issues before parts ever hit the spindle.

Tools & Further Reading

CNC Fillet vs Chamfer Guide

Tolerance Fit Calculator

Hole Pattern Design Best Practices

Coming Soon: “CNC Wall Failures Explained” YouTube video (stay tuned!)

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