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Designing for CNC: the wall-thickness rule that saves a part

Published April 18, 2026 · Updated August 20, 2026

A 0.6 mm wall in 6061 looks fine in CAD and breaks in machining. Here is the rule of thumb we use, with worked examples for aluminium, stainless and plastics.

Why this rule matters

A 0.6 mm wall in 6061 looks fine in CAD. It will deflect, chip and in the worst case break off during machining. Here is the rule we use, with examples for aluminium, stainless and plastics.

Worked examples

  • Aluminium 6061: minimum wall 1.0 mm
  • Stainless 304: minimum wall 1.5 mm
  • POM / Delrin: minimum wall 0.8 mm

 

 

 

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For parts that need to hold fasteners, add at least 2x nominal diameter around the hole.

If you cannot avoid a thin wall, add a small fillet (R0.5) to spread the cutting load.
Now let me do a real save-and-verify test to make sure changes actually persist:

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Designing for CNC: the wall-thickness rule that saves a part | HongChen CNC