How Thin Can You Machine? Wall Thickness Limits and How to Reach Them
Why thin walls deflect, chatter and distort, the realistic minimums by material, and the fixturing, toolpath and stress-relief techniques that make 0.8 mm walls repeatable.
Written by Engineering Team
"How thin can you go?" has two answers. The first is the number: 0.8 mm in aluminium, 1.2 mm in stainless, 1.5 mm in most plastics. The second is more useful: it depends on the height of the wall, how it is supported, and how much you are prepared to pay.
Why thin walls are hard
Three separate mechanisms work against you.
Deflection. Cutting force pushes the wall away from the cutter. The wall springs back after the tool passes, leaving the wall thicker than programmed — and thicker at the top than at the bottom, because deflection grows with the unsupported height.
Chatter. A thin wall is a low-mass, low-stiffness structure with a natural frequency in the range machining excites. Once chatter starts, surface finish collapses and the wall can be permanently deformed.
Residual stress. Rolled and extruded stock contains internal stress from its production. Removing material unbalances that stress and the part moves — sometimes after it leaves the machine, sometimes after it leaves the building.
Realistic minimums
| Material | Practical minimum | With extra process control | Wall height limit |
|---|---|---|---|
| Aluminium 6061 | 1.0 mm | 0.8 mm | ~15× thickness |
| Aluminium 7075 | 1.2 mm | 0.9 mm | ~12× thickness |
| Stainless 304/316 | 1.5 mm | 1.2 mm | ~12× thickness |
| Titanium Gr5 | 1.5 mm | 1.2 mm | ~10× thickness |
| Steel 1045 | 1.2 mm | 1.0 mm | ~15× thickness |
| POM / PEEK | 1.5 mm | 1.2 mm | ~10× thickness |
| PMMA / PC | 2.0 mm | 1.5 mm | ~8× thickness |
"With extra process control" means dedicated fixturing, staged stress relief and a slower finishing strategy. Expect 20 – 40 % more cost for those parts.
What we do to make thin walls work
Staged material removal. Rough to within 1 mm of final, stress-relieve, then finish. For 7075 and titanium this is not optional — it is the difference between a part that holds tolerance and a part that bows visibly on the inspection plate.
Support as you cut. Machine the wall in vertical steps, finishing each band before moving down, so the uncut material below continues to support the section being cut. Cutting full-depth in one pass on a tall thin wall is how walls get scrapped.
Balanced removal. Remove material from both sides alternately where the geometry allows. A pocket machined only on one side of a plate guarantees a bow.
Vacuum and low-pressure workholding. Clamping force itself deforms thin parts. Vacuum chucks spread the load; soft jaws machined to match the part contour support it without point loads.
Sacrificial ribs. Leave temporary ribs across a large thin face, machine everything else, then remove the ribs in a final light pass. Cheap, effective, and invisible in the finished part.
Trochoidal toolpaths. Constant radial engagement means constant cutting force, which means no impulse to excite chatter. Slightly longer cycle time, dramatically better result.
Tuned cutting parameters. Sharp, high-helix cutters with polished flutes, high spindle speed, light radial depth and high feed. The goal is to cut cleanly rather than push.
What you can do in CAD
Keep walls uniform. A wall that steps from 3 mm to 1 mm will distort at the transition. Gradual changes distribute the stress.
Add ribs instead of thickness. A 1.5 mm wall with a 2 mm rib every 40 mm is stiffer, lighter and cheaper than a uniform 3 mm wall.
Add a return flange. A thin wall with a small flange at its free edge is several times stiffer than the same wall without one. This is the same principle that makes sheet metal enclosures rigid.
Limit the height. If you can split a 60 mm tall, 1 mm wall into two 30 mm sections with a step between them, the part becomes far easier to make.
Specify flatness realistically. A 1 mm wall 200 mm long will not hold 0.05 mm flatness free-standing. If the function requires that, it is the assembly that should hold it, with the part constrained.
Tell us what the wall is for
There is a large difference between a wall that must be thin because of weight, one that must be thin for heat transfer, and one that is thin because the model was inherited from a casting. Knowing which it is lets us suggest the right approach: keep it thin and control the process, add a rib, or open it up and save the money.
