Knowledge Base
CNC Machining Design Best Practices
Engineering recommendations for wall thickness, inside corners, holes, threads, and other core design elements
Design Elements
Four Core Design Elements
Master these four core design elements to make your parts more machinable, lower cost, and more consistent in quality.
Wall Thickness Design
- — Aluminum alloy minimum wall thickness ≥ 0.8mm
- — Stainless steel minimum wall thickness ≥ 1.0mm
- — Engineering plastic minimum wall thickness ≥ 1.2mm
- — Height-to-diameter ratio recommended within 4:1
Recommended Value
Recommended wall thickness: 1.5-3mm (optimal)
Design Note
Too thin = deformation risk; too thick = increased material cost
Inside Radius & Corner Relief
- — Inside radius ≥ tool radius × 1.2
- — Bottom radius recommended larger than side radius
- — Corner relief requires extra operations and increases cost
- — Prioritize large radii to reduce machining difficulty
Recommended Value
Recommended inside R ≥ R0.5mm
Design Note
Too small inside radius requires micro tools — low efficiency
Hole Design Specifications
- — Standard drill depth-to-diameter ratio ≤ 5:1
- — Deep hole machining requires gun drilling (≤10:1)
- — Prioritize standard hole diameters: φ1/2/3/4/5/6mm
- — Hole spacing ≥ hole diameter × 1.5
Recommended Value
Leave 0.5mm allowance at bottom of blind holes
Design Note
Non-standard hole diameters require custom tools — longer lead time
Thread Design
- — Metric thread tap drill size reference chart
- — Thread depth ≤ hole diameter × 2.5 (blind holes)
- — Through-hole threads preferred over blind-hole threads
- — Avoid tapping on thin-walled parts
Recommended Value
Recommended 6H/6g accuracy class
Design Note
Excessively deep threads risk tap breakage — higher scrap rate
Design Principles
Four Principles of Good Design
Follow these design principles to reduce machining difficulty and cost from the source.
Symmetry Principle
Design parts symmetrically whenever possible to reduce flip setups and positioning errors.
Unified Datum
Align design datum with machining datum to reduce dimension chain conversion errors.
Avoid Sharp Corners
Internal sharp corners cause stress concentration and cannot be machined — always use radius transitions.
Simplify Geometry
Use the simplest shape that achieves the function — avoid complex surfaces when not necessary.
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