Separate nominal geometry from acceptance limits
A CAD file describes intended geometry; it does not necessarily define the allowed manufacturing variation. Identify which dimensions are critical to function and specify their tolerances in the controlled fabrication drawing. Confirm the supplier’s documented default tolerances for features that do not need a special limit.
Use consistent units and a clear order of precedence between drawings, fabrication notes and data files. A general note should not silently override a connector-specific requirement. Resolve contradictions before quotation is converted into a production release.
Treat different features separately
Finished hole diameter, hole position, slot width, outline position and overall thickness are different measurements. Copper width and spacing also change through the manufacturing process. State whether a requirement applies to the design image, finished copper or another defined inspection condition.
Registration affects the relationship between layers, holes, pads and mask openings. A drill-size tolerance cannot by itself protect annular geometry. Review the full relationship between the relevant features, including the variation that must be accommodated in the design.
Budget the complete interface
For a connector or enclosure, combine board variation with the mating part’s dimensions and assembly conditions. Decide which datum controls alignment. Avoid independently tightening every dimension when a well-chosen datum or a less constrained interface can solve the actual fit problem.
Track width and isolation gap requirements must also account for electrical intent. Manufacturing spacing, controlled impedance and product-level electrical isolation answer different questions. A fabricator’s minimum process capability is not an automatic clearance approval for the finished equipment.
Agree evidence before production
List the critical characteristics, measurement locations, method and sampling requirements. Specify the revision and applicable acceptance documents, including any agreed exceptions. Tighter limits can affect material choices, tooling, inspection and yield, so obtain confirmation before the order is released.
Use first-article measurements to verify the interface and to identify unclear requirements. Record deviations and disposition through the design owner rather than accepting undocumented CAM edits. The inquiry should include the dimensioned drawing, stackup, hole table and a short list of the features that determine successful assembly.