Datum & GD&T validation
Three-datum-feature rule, simultaneous requirement principle, MMC vs RFS callouts, datum-feature-of-size selection, profile-of-surface vs profile-of-line — and the eight signatures of a poorly applied datum frame.
Free Engineering Resource
The Component Design Checklist Every CNC Engineer Should Run Before Releasing a Drawing.
28 pre-release validation points used inside our DfM reviews. Catch tolerance stack-ups, datum errors, unmachinable corner radii and material-spec mismatches before the part hits the shop floor — the failures that quietly add 20–40% to your unit cost.
- ✓ ASME Y14.5 datum & GD&T validation (8 checks)
- ✓ Tolerance budget & stack-up triage (5 checks)
- ✓ Material & heat-treatment specification (4 checks)
- ✓ Geometry sanity — radii, depths, holes, threads (7 checks)
- ✓ Surface, coating & inspection callouts (4 checks)
What's inside the checklist
Tolerance budget & stack-up
How to identify a stack-up before it ships, when to call basic dimensions vs limits, the five most common over-tolerancing patterns, and a reference table of process capability for CNC, VMC and 5-axis platforms.
Material & heat-treatment specs
Grade-and-condition callouts (don't say "aluminum" — say "6061-T6 per AMS-QQ-A-200/8"), case-hardening depth specs, surface hardness vs core hardness, and supply-chain-friendly substitution rules.
Geometry sanity checks
Internal radii vs cutter radius, pocket depth-to-width limits, drill depth-to-diameter limits, thread-relief grooves, undercut viability, fixturing pad allowance — the seven geometric flags that break manufacturability.
Surface & coating callouts
Ra vs Rz vs Rmr, when to call lay direction, anodise vs chromate vs passivation specifications, plating thickness on threaded features, and how to write a callout that the inspector can actually verify.
Inspection & PPAP-readiness
FAI scope decisions, balloon numbering conventions, key characteristic identification, inspection-frequency rules for production runs, and how to specify CMM reports without inflating cost.
Built from 1,000+ DfM reviews.
Every point in this checklist comes from a real drawing our manufacturing engineers had to flag during quoting. Use it once on your next release and you will catch at least one issue that would have cost you a revision cycle.
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