A09 · Reference edition 2026.11
Datum reference frames — Recording and revision
The drawing datum scheme and the physical fixture are related descriptions, not interchangeable objects. Datum precedence affects the intended setup.
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 When information changes, explain the change and retain enough of the earlier description to understand what was superseded.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
Place the drawing reference beside each contact group and mark which face is loaded first.
| Reference record | Interpretation |
|---|---|
| A09 | Datum reference frames |
| Scope and purpose | The drawing datum scheme and the physical fixture are related descriptions, not interchangeable objects. Datum precedence affects the intended setup. |
| Limits and interpretation | A convenient flat face is not automatically a specified datum feature. |
Review checklist
Check the identifier; describe the observation and its source; date the revision; link affected figures; distinguish confirmed facts from open questions.