Context

Not all tolerances are equal. If you treat every feature as critical, cost and lead time spike without improving performance.

Tolerance tiers define inspection scope. Without tiering, you pay for full inspection on low-risk features and destabilize production yield.

The Trap

The trap is using the tightest tolerance on the full drawing. That drives unnecessary inspection and unstable yields.

The Geppetto Take

We tier tolerances: critical features get tight control, important features get moderate control, and cosmetic features get general tolerance. This keeps production stable and predictable.

Evidence / Data

  • Tight tolerances increase inspection time and rejection rates.
  • Tiering reduces measurement load and focuses control where it matters.

Control Actions

  • Define A/B/C tolerance tiers on the drawing.
  • Use CMM scanning only on tier A features.
  • Apply general tolerances to non-critical features.
  • Align tiering with functional datums.

Checklist

  • Tier map defined and shared with suppliers.
  • Tier A features tied to functional performance.
  • Tier B/C features use default tolerances.
  • Inspection plan matches tiering.

What to Send

Send a list of functional features and the performance impact of each.

FAQ

Do tolerance tiers reduce quality?

No. They focus quality control on what actually drives performance.

How many tiers should we use?

Usually three: critical, important, and reference.

Can tiers change after prototyping?

Yes. We often tighten or relax based on pilot results.

CTA

Send a screenshot for a chaos-check.