A13 · Reference edition 2026.11
The 3-2-1 layout concept — Comparison and alternatives
Three, two and one contact groups describe a conceptual constraint arrangement for a suitable rigid part. Contact geometry still needs review.
Scope and purpose
Compare alternatives using the same question and context. A difference in wording, layout or scale is not automatically a difference in performance. Keep the original observations available and explain which differences are meaningful for this comparison.
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 |
|---|---|
| A13 | 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
State the comparison question; align context and labels; list common features separately from differences; leave unsupported conclusions open.