A14 · Reference edition 2026.11
The 3-2-1 layout concept — Recording and revision
Three, two and one contact groups describe a conceptual constraint arrangement for a suitable rigid part. Contact geometry still needs review.
Scope and purpose
A reference record should allow another reader to reconstruct the intended description. Keep the identifier, context and revision together. When information changes, explain the change and retain enough of the earlier description to understand what was superseded.
Working notes
This reference collection concerns light, offline dimensional-inspection layouts. It brings locating concepts, component descriptions and revision records together without substituting for an engineered fixture design. The drawings are original explanatory diagrams. Reference IDs identify documents, not commercially tested products. Read the scope and limitations alongside each example, and keep the actual part drawing and inspection requirements available when reviewing a proposed layout.
Practical example
Sketch three primary supports before adding secondary and tertiary locators.
| Reference record | Interpretation |
|---|---|
| A14 | The 3-2-1 layout concept |
| Scope and purpose | Three, two and one contact groups describe a conceptual constraint arrangement for a suitable rigid part. Contact geometry still needs review. |
| Limits and interpretation | Thin walls and flexible parts need analysis beyond the rigid-body sketch. |
Review checklist
Check the identifier; describe the observation and its source; date the revision; link affected figures; distinguish confirmed facts from open questions.