A21 · Reference edition 2026.11
Probe access — Definition and boundaries
A nominally clear measured feature may be inaccessible along the probe approach or withdrawal path. Include the whole inspection movement.
Scope and purpose
Start by separating the named concept from adjacent concepts. Use the observation below to identify the question the record is intended to answer. Read the caution before applying the example. A definition is useful only when another reader can tell what falls outside it.
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
Draw the approach envelope as a separate translucent region around the target feature.
| Reference record | Interpretation |
|---|---|
| A21 | Probe access |
| Scope and purpose | A nominally clear measured feature may be inaccessible along the probe approach or withdrawal path. Include the whole inspection movement. |
| Limits and interpretation | A static sketch does not prove collision-free operation on a particular machine. |
Review checklist
Write a one-sentence scope statement; identify a neighbouring concept; record what the example does not establish.